First Light and review of the Sharpstar EDPH II with 0.8 Reducer Flattener
This is a review of the Sharpstar EDPH II with the 0.8 Reducer Flattener attachment. This will also show undersampling isn’t as much of an issue as it is made to feel and how to get around it.
The sharpstar EDPH II is a short wide field scope with triple-lens, one of which is ED (Extra-Low Dispersion) glass although Sharpstar has not mentioned which type of glass it used with this scope and going by the price, I'd imagine this would be the cheaper PFL-51 type glass (if it was FPL 53 it would be a lot more expensive and closer to the price of Esprit from Skywatcher). It is coloured Red and White with a retractable dew shield and comes with a red cover for the lens. The whole scope is made from metal and has a sturdy feel to it.
The following stats for the scope are the following:
The sharpstar EDPH II is a short wide field scope with triple-lens, one of which is ED (Extra-Low Dispersion) glass although Sharpstar has not mentioned which type of glass it used with this scope and going by the price, I'd imagine this would be the cheaper PFL-51 type glass (if it was FPL 53 it would be a lot more expensive and closer to the price of Esprit from Skywatcher). It is coloured Red and White with a retractable dew shield and comes with a red cover for the lens. The whole scope is made from metal and has a sturdy feel to it.
The following stats for the scope are the following:
- Focal length：335mm
- Aperture size：61mm
- Tube length：235mm (disregarding the dew shield)
- Limiting visual magnitude：10.7
- Accessories： one tube ring, one dovetail plate, one handle
- Focal ratio：f/5.5
- Tube outer diameter：80mm
- Resolution：1.93 arc second
- Net weight：1.42kg (without tube ring and dovetail plate)
- Objective type： doublet air-spaced APO (including an ED glass)
- Gross weight：1.8kg (with tube ring and dovetail plate)
- Reduction factor：f/4.5
- Image circle：44mm
- Lens： Three element
- Outer diameter：66mm
- Back-focus：55mm (can be extended to 99mm)
- Length：287mm overall length with the dew shield retracted
- Coating：full-surface multi-layer coating
- Weight：0.45kg additional weight making it overall 2.25kg.
Obviously, This isn’t all of the equipment you will use with this setup, it has a shoe slot for a guide scope and a section for the carry handle which is supplied which other accessories that can be attached (or like me Velcro). The dovetail rail used to connect to the mount would need to be changed, due to the additional weight this will use. This set-up has a 180mm dovetail rail connected which is primarily at the rear of the scope since this is where the centre of balance will be. To add this to the scope, you will need to turn the setup 180 degrees to allow the rail to extend far enough not to interfere with other parts of the scope.
Instead of the handle, I used heavy-duty Velcro due to using the ASIAir on other devices which I Velcro too. This made it a convenient location to attach the ASIAir without it getting in the way at the expense of not using the carry handle. Although, if you use this setup, there are shoes which are designed to be used with the ASIAir which will mount on the handle.
This Scope will set you back £525 for the scope and an additional £205 for the reducer flattener. (Compared to William Optics Zenithstar 61 II APO - £579 + £209 for the field flattener and Skywatcher 72ed DS PRo £349 + £81 for the OVL Flattener or £218 for the flattener reducer)
Instead of the handle, I used heavy-duty Velcro due to using the ASIAir on other devices which I Velcro too. This made it a convenient location to attach the ASIAir without it getting in the way at the expense of not using the carry handle. Although, if you use this setup, there are shoes which are designed to be used with the ASIAir which will mount on the handle.
This Scope will set you back £525 for the scope and an additional £205 for the reducer flattener. (Compared to William Optics Zenithstar 61 II APO - £579 + £209 for the field flattener and Skywatcher 72ed DS PRo £349 + £81 for the OVL Flattener or £218 for the flattener reducer)
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The scope comes with a 10:1 fine-tune focuser, which won’t be used directly to focus due to the Electronic Auto Focuser (EAF), but for manual and fine-tune focusing these are a dream. I did have a small play with it and it felt smooth and well-made. For Astrophotography, I use a ZWO EAF to focus automatically periodically throughout the night. This, make the whole process painless and generally (in basic terms) lazy. Soon as the equipment is hooked up and Polar alignment is done, the majority of the process from this point is automated.
In addition to the above items, I use a 0.8 reducer flattener from Sharpstar, which is designed for this scope. Previously there have been reports of Chromatic Aberration, in the form of harsh, odd-coloured halos around blue bright stars. This for me hasn’t been the case as you will see during the review. This reducer flattener helps the curvature of the lenses, flattens the field to stop elongated stars at the edges of the field of view and also widens the FoV and reduces the Focal Ratio, which is key in AP reducing the F/ratio from 5.5 to a fast 4.5. Note the brass screws in the pictures on the reducer (Below). Loosen these for camera rotation, just don't forget to tighten them back up once you are happy with the camera angle, or they could potentially move during the night. |
Sharpstar front lens after its first night out. This was a clean lens before it was taken out! My location is notorious for dust.
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Sharpstar setup with all the equipment attached.
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Same as the left picture. Note the focuser is upside down to help get everything on. Also note the new longer rail.
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This setup will include the following:
- Sharpstar EDPH II
- Sharpstar EDPH Reducer flattener
- Extended rail
- ZWO EAF v2
- ASIAir Pro with V2.1 installed
- ZWO 30mm guide scope
- ZWO ASI 120mm mini guide camera
- ZWO Asi 533mc pro with adequate 55mm backspacing
- Optolong L Extreme 1.25” filter which is threaded in the 11mm back spacer.
- Skywatcher EQ 6 r pro
- USB-powered dew heaters for the guide scope and main scope.
- Fox Halo 96k power bank to power the whole setup apart from the dew heaters which had their own power banks.
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The setup is quite fast to put together. Technically you can have the whole setup put together all the time and you just attach it to the mount (It is that compact), turn everything on and you are near enough good to go. But for the first time setup, this was very simple, apart from the fact I don’t have the correct filter wheel or filter drawer forcing me to use the backspacing which came with the camera. This means I had to install the 1.25” filter before PA, which isn’t in my normal routine. (I generally use a UV IR filter in a filter drawer/wheel to help with PA before moving to Narrowband) and also meant I can’t remove it during the night to either take colour stars or change targets to Broadband targets. But for this test, this wasn’t really an issue or a concern, as I was testing the capabilities of the scope. Since I use the ASIAir all the time, due to going out to a remote B4 location, this is not new to me. I just reset the main camera focal length to 0 and let the Air calculate the correct focal length.
There is also a nice touch on the reducer flattener. unscrewing the back end of the reducer reveals an M48 thread to which you can screw a 2" filter. Although care needs to be taken as this tight space begs for the filter glass to be touched by fingers or damaged if using other objects other than fingers to thread the filter in. It is a nice touch, and handy if you don't have a filter drawer, but purchasing a filter drawer or filter wheel for the ease of changing filters during the night is recommended. |
M48 thread inside the reducer. Simply unscrew the end to reveal the thread. It can also be seen from the external threaded end where you connect the camera.
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One thing to note is the orientation of everything between the stock picture and my setup. The original dovetail plate is very short and this will need to be replaced with a longer dovetail plate or you won't achieve balance on the mount which is essential for guiding. Soon as you put the field flattener, guide scope, ASIAir, camera and the necessary back focus, the centre of balance will be further back, near enough under, or just past the focuser (see picture above). If you intend to do AstroPhotography with this setup, make sure you purchase a longer dovetail plate with it I use a 7" (180mm) rail which seems to work well.
Attaching the rail is simple enough but you will have to rotate the setup nearly 180 degrees for the rail to fit without catching the focuser barrel which connects to the scope. Align the handle (or the flat rectangle part where the handle connects to, (The Velcro part in the picture)) with the centre part of the focuser barrel and adjust to suit from there. You will want it to skim over the fine tune knobs of the focuser (there will be about an 8-10mm gap between them, depending on your setup and orientation of equipment) You can orientate this to your liking and can locate the handle and guide scope shoe anywhere you want due to the Dovetail rail bar underneath. What works for one, may not work for another, so spend some time playing with the setup before the night out to find the best orientation you like which is best for you and your setup. |
Orientation of the scope with the new longer dovetail attached, requiring the setup to be rotated to avoid clashing of equipment.
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Overall I had a 5kg and a 2.5kg weight connected to the mount which was pushed up next to the mount (this is generally recommended anyway as it helps tracking), but I feel I could have gotten away with a single 5kg weight and moved the weight further down. This put the estimated weight at about 4-4.5kg overall.
PA was again not an issue, as well as setting up guiding. Focusing was a little strange as it wasn’t creating a graph while calibrating. It still focused on the stars and wasn’t really an issue, to be honest.
PA was again not an issue, as well as setting up guiding. Focusing was a little strange as it wasn’t creating a graph while calibrating. It still focused on the stars and wasn’t really an issue, to be honest.
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Overall, the scope is small compact, and generally light (until you have every accessory on this earth on there). Focus wasn’t an issue and guiding, again, wasn’t an issue. The colour is quite pleasing (this a personal thing TBH, not everyone will like the colours) and the colours, if you are worried about matching, don’t collide with the ZWO family and focal Reducer Flattener.
The downsides are the dew shield is a little loose. It wobbles side to side in my hand and moves back at certain angles while in my hand. During the night, I never noticed any movement in the dew shield and this is mainly due to it not moving aggressively while guiding, even with the dew heater which can be seen in the picture to the right. As mentioned above, the lens, I feel is FPL-51 glass, solely from the price point. This isn't a bad thing, most scopes use this type of glass, it is just Sharpstar do not disclose what glass is used, but it is a triplet with one of the lenses being Extra-low Dispersion, ED glass. The focal length of the scope favours the smaller pixel size in the camera for good seeing. Cameras with a pixel size between 1.0 and 2.5um will fall in the green line and won't be under-sampled. As mentioned, and demonstrated below, being under-sampled is not too much of an issue, but drizzling does increase the size of the file. So far I am happy with this scope, the dew shield didn't really pose an issue for me during the night, so let’s move on to the pictures, processing, and overall thoughts about the target I chose to test this little scope out. To test this scope I chose the Elephants Trunk Nebula – IC1396. This target has a combination of a bright and faint nebula in the Hydrogen wavelength, dark nebula, and plenty of stars to test this scope out. This target isn’t overly hard to capture but does have a lot of faint sections which will test the focal ratio and how fast it collects data. |
Sharpstar at work. On the EQ R pro mount from Skywatcher. Bit over kill but it got the job done.
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The night
Overall, I took 2.5 hours of data at 300-sec sub-exposures (5mins), dithering every three frames. The focuser was set to refocus at every 1-degree temp change, on any new target and every hour. (TBH these settings are extreme for this type of scope as these are set for the RASA) The data was taken up to the meridian to avoid the flip and another session will be added at a later date to test the longer exposure time results. Flat frames, which comprised 60 frames which I let the ASIAir calculate, were taken on the night for this target and the rest was used from the calibration library.
The night conditions were good, it was a clear sky with a small amount of cloud in the sky, the average temperature was around 1-1.5C, the moon’s phase was in the crescent stage at about 25-30% and by the time I started taking exposures, it was about 30 degrees in the SSW and wasn’t causing any issues. The wind was around 15mph with no wind break around the mount and guiding was around 0.6-1.0 depending on the wind.
The night conditions were good, it was a clear sky with a small amount of cloud in the sky, the average temperature was around 1-1.5C, the moon’s phase was in the crescent stage at about 25-30% and by the time I started taking exposures, it was about 30 degrees in the SSW and wasn’t causing any issues. The wind was around 15mph with no wind break around the mount and guiding was around 0.6-1.0 depending on the wind.
I arrived at the location around 8 30ish and was set up by 9 PM. Photos started at 9 27 and the night finished (for other reasons) around 12 30am. During this time there weren’t any issues nor any hiccups and the night went smoothly, leaving me wondering around thinking if Saturday night was a good night to start videoing for the YouTube channel.
The Results and comparison
With the 2.5 hours of data collected, there will be a comparison between data sets at different drizzle settings, showing stars and data. 2.5 hours on an F4 isn't a lot but this is just to test the scope and its abilities. Further exposure time will be added and this will be amended accordingly.
Overall, the total data - 30 x 300-sec sub-exposures at gain 101, -10C, dithering every 3 frames.
After stacking the image files size changed dramatically with the following sizes:
The larger the file the slower it is to process (something to keep in mind). All processes were the same though out, they all had the same curves applied to each picture, the same process throughout, each picture had the same to keep this even and fair – the only difference was in the stretching of the pictures with the PSF file to find the stars, the star sizes were obviously different and that had to be treated individually or the picture would have had an unfair disadvantage. The following process was used for all three pictures:
Overall, the total data - 30 x 300-sec sub-exposures at gain 101, -10C, dithering every 3 frames.
After stacking the image files size changed dramatically with the following sizes:
- No drizzle – 51.7MB
- 2x drizzle – 207MB
- 3x drizzle – 400MB
The larger the file the slower it is to process (something to keep in mind). All processes were the same though out, they all had the same curves applied to each picture, the same process throughout, each picture had the same to keep this even and fair – the only difference was in the stretching of the pictures with the PSF file to find the stars, the star sizes were obviously different and that had to be treated individually or the picture would have had an unfair disadvantage. The following process was used for all three pictures:
- BlurXTerminator
- NoiseXTerminator
- STF stretch using the Histogram transformation.
- Removed the stars with StarXTerminator
- Curve stretch with RGB/K, L and saturation settings
- Dark Structure Enhance
- Pixelmath to add stars back in the picture
- SCNR to remove the Green from the picture
- EZ star reduction to reduce the stars
- Custom dynamic crop to remove artefacts from dithering
- Saved at 100% in JPEG file format
This is a very basic process for this review designed to keep it linear as possible. The aim wasn’t to get a perfect picture but to test the parameters of the equipment and settings to see the final result of the picture. This, of course, will lead to a final picture which I would spend a little more time over, but all other processes needed to be completed before the final picture. The only limiting factor is the overall exposure time on the target.
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Calculations show this setup with the Sharpstar EDPH II, Reducer flattener and the 533MC is undersampled which would lead to blocky stars when zoomed in and in extreme cases blocky stars when it’s fully zoomed out. In this instance, the stars weren’t too bad, it shows only marginal under-sampling and the overall picture looked ok, but zoomed in the stars were blocky.
Stacking the pictures in each drizzle setting (x0, x2 and x3 drizzle) was generally fast and this could be down to the lack of data. Being only 30 pictures at 300-second exposures would be the reason why it was fast. Stacking lasted no more than 5 mins with the software using the full capability of the PC. |
Camera suitability - https://astronomy.tools/calculators/ccd_suitability
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Processing the pictures, using the above process for all three pictures using the same curve to keep the testing fair and in line with each other. As mentioned above the only difference was the noise and deconvolution processes which were individual to the pictures due to the size of the files and pictures.
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Overall the scope is quite fast optically, small, and compact. This will fit in a small case/ bag for storage, but the weight of the scope requires it to be on an EQ5 pro mount at the minimum, with recommendations of at least an EQM 35 pro mount (maybe an EQ5 mount but it will be hitting the limits of its tracking capability for AP), especially when using additional gear, like filter wheels, EAF and guide cameras etc.
Undersampling, while present, is not really a factor when you account for drizzling the data in stacking. With drizzling most cameras can be used without issue. The FoV is wide and even more so when used with a 4:3 or APS-C-style camera. |
FoV based from https://astronomy.tools/calculators/field_of_view/
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Previously there were reports of this scope having Chromatic Aberration. Large blue/ purple halos around stars could not be calibrated or processed out and only got worse with stretching the data. Chromatic Aberration was seen with this scope with the reducer flattener and the FoV was flat all the way to the edge of the camera.
The Chromatic Aberration in this scope was quite harsh but only in the Broadband targets, while using the UV/IR filter. I have ruled out the filter since I have used it on multiple scopes and have more than one filter. I have contacted Sharpstar for advise on this issue. |
Chromatic Aberration in the stars, showing as a purple-hued colour.
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The pictures below show post-stretch pictures. There is minimal difference between all three when scrolling out and viewing the picture like this. But when you zoom in on the picture, things are very different when you look at the stars. They are very blocky, which comes from under-sampling, which gets better as you drizzle but you won't notice zoomed-out on the picture.
IC1396 x3 drizzle
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IC1396 no drizzle
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IC 1396 x2 drizzle
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IC 1396 drizzle comparison. Left: No drizzle. RIght; x3 drizzle
IC 1396 star comparison: x2 drizzle
This scope’s price is in the mid-range of other similar scopes, E.g., Skywatcher 72ed and the William Optics 61 II APO reflector. And holds well against both scopes but without having the WO 61 to hand to compare it to the Sharpstar. Overall, this is a small compact scope which is built with half-decent features which will blow the Skywatcher 72ed out of the water and also will give the WO a run for its money. But I have a feeling this and the WO will butt heads with more people preferring the WO. Although the WO and Skywatcher are both doublets, the price range of this scope puts these as immediate competitors to this scope.
Would I buy this in place of a Skywatcher 72ed and reducer? Yes. It is smaller, has a slightly wider FoV and has better optics. But I would question if the scope has Chromatic Aberration which appears to be in alot of scopes which is caused by the primary lens at the front of the scope.
Questions and Answers
Is this beginner friendly? Yes, Definitely
Do you need all the equipment I used on it? No, definitely not. You can manually focus without issues; guiding is always preferable in mind. A field flattener is not necessary, but you will have elongated stars in the corners/ edges due to the glass which is a little extreme.
Is this a visual scope? Yes – it can be used as a visual scope and AP scope.
Does the FPL glass make a difference in this scope? It greatly reduces the price. But overall I don't think it affects the scope. If it had the higher-end glass in, this would be a competitor of the Esprit and variants of this type of scope due to the price range.
Would I buy this in place of a Skywatcher 72ed and reducer? Yes. It is smaller, has a slightly wider FoV and has better optics. But I would question if the scope has Chromatic Aberration which appears to be in alot of scopes which is caused by the primary lens at the front of the scope.
Questions and Answers
Is this beginner friendly? Yes, Definitely
Do you need all the equipment I used on it? No, definitely not. You can manually focus without issues; guiding is always preferable in mind. A field flattener is not necessary, but you will have elongated stars in the corners/ edges due to the glass which is a little extreme.
Is this a visual scope? Yes – it can be used as a visual scope and AP scope.
Does the FPL glass make a difference in this scope? It greatly reduces the price. But overall I don't think it affects the scope. If it had the higher-end glass in, this would be a competitor of the Esprit and variants of this type of scope due to the price range.
This scope was a nice change to my usual setup. The biggest thing for me is F/ratio. The UK weather is hit and miss and getting clear nights can be few and far between which is why I primarily use the RASA. But this scope will be used on my smaller mount with a mono camera (Either 1600mm or 533mm - I haven't decided yet) for the wide field pictures, where it will be set up and left all night on one target.
This scope is a good scope until you hit the Chromatic Aberration. So Narrowband targets are fine (as seen throughout this review) , but Broadband targets are hit and miss. See my review on the updated version of this scope.
This scope is a good scope until you hit the Chromatic Aberration. So Narrowband targets are fine (as seen throughout this review) , but Broadband targets are hit and miss. See my review on the updated version of this scope.
IC1396 2.5 hours total exposure at 300-sec sub-exposures using the Optolong LeXtreme 1.25" filter.