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Has anyone heard of this scope before (Sharpstar 61 EDPH)?

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250 replies to this topic

#226 Poochpa

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Posted 11 November 2020 - 10:13 AM

Beautiful image, Gary. That's a very nice looking finder scope on your TEC. :)

Mike



#227 gnarayan

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Posted 11 November 2020 - 02:52 PM

Also been working on Heart and Soul, but been using the AT115 more recently. I want to start on Pleiades and Jellyfish with the Sharpstar when it's clear next.

 

50557016948_8773f07b7f_b.jpg


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#228 leemajors

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Posted 17 November 2020 - 08:05 AM

I recieved my 61EDPH ii a few days ago, along with a new camera the ZWO533mc.

I have had 1 clear night with it and am pleased with star shapes into the corners, however I noticed a large amount of purple fringing on bright stars in combinations with the 533 and my Idas P2 LPS filter.

I switched over to my Astronomik CLS ccd filter and fringing was gone.

I know the CLS has a stronger blue cut at 450nm vs 420nm for the Idas, but ive never noticed fringing on my other triplets using the Idas, but that was with my old Atik428osc that I no longer own.

Has anyone else noticed this, im not sure if the EDPH II has very bad colour correction ( that would be disappointing as its a Triplet as I bought it specifically for OSC imaging of broadband targets ), or if the new camera is especially sensitive to UV and for some reason the Idas isn't blocking UV properly. 

I will have to try the new camera on my other triplets and see if I get the same, and also try using a simple Baader UV/IR Lum filter with the Sharpstar to see if that helps.

Here is side by side comparison, Idas P2 filter on the left and CLS on the right

Lee

Attached Thumbnails

  • Screenshot 2020-11-17 at 13.14.53 copy.jpg
  • Screenshot 2020-11-17 at 13.28.43 copy.jpg

Edited by leemajors, 17 November 2020 - 08:30 AM.


#229 leemajors

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Posted 18 November 2020 - 10:00 PM

Update I tried the new camera on my TS80 triplet tonight with the same Idas filter and got no blue fringing, then I tried the Baader UV/IR Lum filter on the sharpstar but still got the blue fringing. Lastley I removed the reducer and did the tests again, hardly any blue fringing. so it appear the dedicated reducer is introducing the blue fringes. Im now wondering if when the upgraded the optics from doublet to triplet in the Mk II, did they also update the reducer to match or not? when I was waiting for my uk supplier to receive stock scope I think he said he still had plenty of the reducers, if they did make any changes to the reducer for the triplet I guess its possible I received an old one. Ive just sent Sharpstar a message to ask them if there are 2 versions of the reducer or just 1.

Lee


Edited by leemajors, 18 November 2020 - 10:00 PM.


#230 UKalwayscloudy

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Posted 19 November 2020 - 05:46 PM

Pretty sure the reducer is unchanged. I think depending on filter I have had fringing but it was removed using the Lightroom tool.

#231 kel123

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Posted 19 November 2020 - 05:58 PM

I doubt that they changed the reducer. A vendor I communicated with, is selling the same reducer for both versions.

#232 leemajors

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Posted 20 November 2020 - 05:14 AM

Pretty sure the reducer is unchanged. I think depending on filter I have had fringing but it was removed using the Lightroom tool.

yes sharpstar have confirmed this now, 


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#233 UKalwayscloudy

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Posted 21 November 2020 - 03:55 AM

I’m now trying out the adjustable Altair 1.0 flattener which is designed as a generic flattener for f5 to 6. As a first step got it linked to my Nikon Z6 and the 61EDPHII just fine. Infinity focus at frame centre achieved easily and there is plenty of independent adjustment of Backfocus and overall focus. First step is the extent of focus peaking region on distant trees. Then star fields. I’ll report back but don’t hold your breath on stars as the weather is rubbish for a while!

#234 UKalwayscloudy

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Posted 21 November 2020 - 07:15 AM

Here is the second stage tree test. After some fiddling with some spacers and the adjustment on the flattener I went outside for my tree test.Horrible grey drizzly day. Some small adjustments got me focus peaking across the full frame and I took some test shots of a distant tree, on full frame (FX). This is the top right aproxx 1/6 linear fraction so this rectangle is 1/36 of the total image on a 36x24mm sensor). I focused on the middle of the frame and the corner of FX looked like this. So this is beyond the corner of the APS-C region. Of course, this is just telling me that there is decent flatness and no hideous CA. Star shapes are away harder test, but it hasn't failed this stage. Now I need to wait for a clear night. 

Attached Thumbnails

  • TreeTopRightSixth - 1.jpeg

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#235 UKalwayscloudy

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Posted 23 November 2020 - 10:36 AM

OK, so it now looks like the Altair variable 1.0 flattener is a good option for the 61EDPH II to work at its native focal length. There are a few pictures to show so I will do this in bits. 

 

First the item I am talking about is the one here::

 

https://www.altairas...tener-292-p.asp

 

which is an affordable but quality piece of optics. It fits by default by a 2in nose piece. So the basic way to attach it is via the 2in adapter that comes with the scope that would be used for pure visual work with a 2in diagonal. This is easy to fit together at the telescope end. I might explore a screw connection later, as the fit is not that snug. It's OK if you place and tighten it symmetrically. The other end by default is an M42 or standard T2 screw fitting. In my tests I attached it to the Baader UFC gear and then via a wide T ring to my full frame Nikon Z6. I also had a 2in filter in my UFC for the test. 

 

Something to note about this adapter is that it's variability is in the camera side extension. So in effect it is a widely adjustable back focus adapter. When I ordered it I did wonder if the adjustability was in how much it burrowed into the focuser, but it's the other side. But - the glass for the flattener sits right up to the end of the focuser (previous ones I tried were some way off). 

 

First - illumination. It illuminates well to full frame 36x24. It does not do quite as well as the standard factory 0.8 reducer, which an Aus firm measured as having less then 4% fall off by the full frame corners. You DO need flats now to work at full frame with the 1.0 Altair, even if your sensor and filters are scrupulously clean.  Fall off is mild in the SOC form, as shown in the picture, but that becomes a thing when it is stretched. I have to apologise as I did not take my flats at around the same time as the imaging, so there are some blobs in one but not the other (very wet outside last night) so the corrected images will still have some blobs. Ignore that as it is nothing to do with the flattener and everything to do with my scrappy technique.

Attached Thumbnails

  • Flat.jpg

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#236 gnarayan

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Posted 23 November 2020 - 11:05 AM

OK, so it now looks like the Altair variable 1.0 flattener is a good option for the 61EDPH II to work at its native focal length. There are a few pictures to show so I will do this in bits. 

 

First the item I am talking about is the one here::

 

https://www.altairas...tener-292-p.asp

 

which is an affordable but quality piece of optics. It fits by default by a 2in nose piece. So the basic way to attach it is via the 2in adapter that comes with the scope that would be used for pure visual work with a 2in diagonal. This is easy to fit together at the telescope end. I might explore a screw connection later, as the fit is not that snug. It's OK if you place and tighten it symmetrically. The other end by default is an M42 or standard T2 screw fitting. In my tests I attached it to the Baader UFC gear and then via a wide T ring to my full frame Nikon Z6. I also had a 2in filter in my UFC for the test. 

 

Something to note about this adapter is that it's variability is in the camera side extension. So in effect it is a widely adjustable back focus adapter. When I ordered it I did wonder if the adjustability was in how much it burrowed into the focuser, but it's the other side. But - the glass for the flattener sits right up to the end of the focuser (previous ones I tried were some way off). 

 

First - illumination. It illuminates well to full frame 36x24. It does not do quite as well as the standard factory 0.8 reducer, which an Aus firm measured as having less then 4% fall off by the full frame corners. You DO need flats now to work at full frame with the 1.0 Altair, even if your sensor and filters are scrupulously clean.  Fall off is mild in the SOC form, as shown in the picture, but that becomes a thing when it is stretched. I have to apologise as I did not take my flats at around the same time as the imaging, so there are some blobs in one but not the other (very wet outside last night) so the corrected images will still have some blobs. Ignore that as it is nothing to do with the flattener and everything to do with my scrappy technique.

This is fabulous news - many thanks for this testing.



#237 UKalwayscloudy

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Posted 23 November 2020 - 12:48 PM

Next, how does the image look and what are the star shapes like? I'm sitting here waiting for astrometry.net to return an analysis. Meantime, let's look first at a crop of the full frame image to the size of a 4/3 sensor like my Altair 269c that I am likely to use the most. So I've basically cropped to the central 1/4 by area. Then I show the full cropped image. Basically, apart from a rotation, it looks more or less the same as that on astronomy.tools with 335mm focal length and an ASI1600. So the FOV view is about right. Pay no attention to overall IQ and my blobs. It was very wet last night and I did not do my flats till this morning. First the whole 4/3 sensor image (feel free to check M31 on the tools FOV link).

Attached Thumbnails

  • Flat43 - 1 (1).jpeg


#238 UKalwayscloudy

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Posted 23 November 2020 - 12:51 PM

And here is the crop to 200% of a corner of that previous pic. As far as I can tell this is fine in terms of circularity. I should say I was a bit rushed and did not guide either. I have not done anything to manage halos either. So basically I think there is no problem using this 1.0 flattener with the scope at its native focal length with something like the ASI1600M, Altair 269c and similar 4/3 sensor cameras from QHY et al. 

Attached Thumbnails

  • Flat43crop - 1.jpeg


#239 UKalwayscloudy

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Posted 23 November 2020 - 12:54 PM

I need to do something else for a while now but will come back to APS-C and full frame. Please note that I have NOT done a detailed optimisation of the backfocus spacing, but just used the setting I found gave me best edge to edge  focus peaking while shooting the tree in my earlier experiment. I think it the optimum is probably within 1cm as the focus peaking on my tree weakened a bit with such changes. 



#240 UKalwayscloudy

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Posted 23 November 2020 - 02:53 PM

Now the DX crop (similar to APS-C). This is what you would get from Hypercam 26C, ASI2600, ASI071 etc. Field of view is now obvious but I'll show it!

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  • FlatBasicDXsmall.jpg


#241 UKalwayscloudy

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Posted 23 November 2020 - 03:00 PM

Now two corner crops. I'll show two. This is the point at which I think my positioning of the 2in nose piece might have been at fault. I think there is a bit of tilt showing as the bottom right 200% crop is fine but the top right crop is showing signs of being at the wrong distance. If you look at the image as a hole this type of problem is only at the level of detailed pixel peeping, so I am not personally concerned. Now I've seen this I'll revisit the issue of how I insert the flattener or whether I can screw it in by removing the nosepiece. 

Attached Thumbnails

  • APSCTR - 1.jpeg
  • APSCBR - 1.jpeg


#242 UKalwayscloudy

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Posted 23 November 2020 - 03:08 PM

Finally the full frame FX (36x24). I'm showing this first just to point out that with flats you can get a good evenly illuminated image across the larger sensor that you would have in a Nikon FX, or ASI6200 type sensor. The impact on an image like this from the corner imperfections is more of an issue. If you are only going to print out small or put on social media it is irrelevant. If you want detailed high quality output you might not think it is up to the job. Personally, I have seen a lot worse on quite expensive camera lenses. 

Attached Thumbnails

  • FlatBasicFullSmall.jpg


#243 emr7

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Posted 23 November 2020 - 03:38 PM

Finally the full frame FX (36x24). I'm showing this first just to point out that with flats you can get a good evenly illuminated image across the larger sensor that you would have in a Nikon FX, or ASI6200 type sensor. The impact on an image like this from the corner imperfections is more of an issue. If you are only going to print out small or put on social media it is irrelevant. If you want detailed high quality output you might not think it is up to the job. Personally, I have seen a lot worse on quite expensive camera lenses. 

This great thanks, would it be possible to get some pictures of how it is attached, how would get proper backfocus on a camera like qhy294, etc?



#244 UKalwayscloudy

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Posted 23 November 2020 - 06:56 PM

Yep will do. Pics and numbers to follow allow with last crop tomorrow.

#245 UKalwayscloudy

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Posted 24 November 2020 - 04:48 AM

Astrometry.net processed that last image for me now and came back with size 6.06 by 4.03 deg. If my maths is right this an 343mm focal length equivalent. Finally the bottom right 200% crop. The stars have got noticeably deformed by the far corner, but are ok by the top left corner of that cropped region. You can see where that crop corresponds to in the main image. Top right is slightly worse, but I need to sort out the tilt and fine tune the spacing. Anyway, that's it for now on image quality. I'm very happy with this flattener as I'm either shooting with a 4/3 sensor in my 269c and on full frame am often doing square crops. I'll come back to this in a bit and try to fine tune the fitting and space, so please regard these photos as worst case. That flattener is about £100 GBP by the way. 

Attached Thumbnails

  • FXBR2 - 1.jpeg

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#246 UKalwayscloudy

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Posted 24 November 2020 - 04:56 AM

Now for setup and spacing. First of all here is the rig it was tested on, fully assembled. The flattener has a 2in nosepiece that gets inserted into the 2in attachment on the 61EDPH II. The flattener terminates in a std T2 male thread (see next post). Now in my test rig that T2 is connected to some Baader adapters allowing me to use their UFC filter system. That particular choice is not significant. It ends in a Nikon Z adapter that connects to my camera. 

Attached Thumbnails

  • SetupCN.jpg


#247 UKalwayscloudy

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Posted 24 November 2020 - 05:15 AM

Here are the key parts disconnected. Now for the spacing, I do not think it is helpful to quote "the back focus" needed for this system, for three reasons:

1. The camera side of the adapter is adjustable

2. The only fixed point is the rear side of the glass on the flattener, and it is a bad idea to measure onto glass!

3. I don't want to discourage experimentation. My own numbers based on a crude initial estimate from my tree might be off. 

 

So I suggest the following:

 

Work out, for whatever contraption you can make with whatever spacers or adapters you have to hand, the sum (in mm)

 

S = Reading + Adadpters + Flange

 

Where

 

Reading = Reading on the flattener scale

Adapters = sum of the distances of any spacers including T ring if used

Flange = your camera flange distance

 

In my case, based on focus peaking on distant trees, I used

 

Reading = 75

Adapters = 39

Flange = 16 (The Nikon Z flange distance - my astro cam has 17.5 for that, and many astro cams come in at 17.5 or 12.5 or something like that). 

 

So for me S = 130mm. I reckon it is should be between 120 and 140, but please experiment if you try this. I can't help noticing that 39+16=55, coincidentally the distance often quote for a DSLR and T ring. So if you use a trad DSLR, a T ring with no other spacers maybe start with around 75 on the dial. Just a thought. That 39mm was just the thickness of what I threw together. I did not target it to get 55mm. 

 

Note that it is that TOTAL S that you should work from. You can have more in adapters and a lower reading. If we get this nailed down to higher precision maybe we can think about filter corrections. I did this with an IDAS 2.5mm filter in the UFC so maybe you want 0.83mm less with no filter. That is irrelevant precision right now. 

 

Note that S is the distance from the rear of the glass of the flattener to the sensor, with some fixed constant added in. That constant might well be 55 but I'm not presuming that to be right. What's important is to find out the best value of S. My 130 is a crude initial estimate to be clear. 

Attached Thumbnails

  • SetupExpl - 1.jpg

Edited by UKalwayscloudy, 24 November 2020 - 05:20 AM.


#248 UKalwayscloudy

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Posted 24 November 2020 - 06:23 AM

OK, so this is the last post before further testing with the astrocam in the pic. This is an Altair Hypercam 269c with a 17.5 mm distance from sensor to the T2 thread base. This is a common distance for many astro cams, along with 12.5mm. The QHY294 appears to be 17mm +-0.5 so given that we do not have precise numbers this set up will do for emr7's question. For an astro cam I have removed the T ring and my adapters are basically a T extension tube with a filter tray in the middle. You can use ANY T extender thingy (unless you want a wider optical path like wide T - I am not there yet) and there is a filter holder within the flattener. 

 

My extension rig includes a filter tray (UFC) and its optical length is 45.5mm. My camera internal distance is 17.5mm so according to the formula I need the flattener adjusted to 67mm. That is shown in the picture. 

 

To give a specific answer to emr7. His camera internal distance is nominally 17mm, so what is needed for that is that 

 

setting on flattener + length of T extension  = 113 +/- 10 mm. 

 

There are many off the shelf parts for extenders that would make that easy. I know Altair do a 30 and 20 for not much £. 

 

So I am shutting up now. When I get some pics with that Hypercam I'll give some examples. Later I might start taking the flattener to bits and see what can be done using the internal threads at both ends to either widen the optical path or make more secure. I'll also go back to full Frame and maybe step through some finer distances to see if it can be improved in the corners with some adjustment to that 130. If anyone thinks I have got the wrong numbers and it is better at 125 or something please let me know!

Attached Thumbnails

  • SetUpAstroCN.jpg


#249 Cometeer

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Posted 25 November 2020 - 08:02 PM

Someone had asked me for this a while ago, but I couldn’t find who it was. Anyway, here’s the ZWO EAF attached to the Sharpstar with a belt drive. No real advantage of this over the shaft coupler; I did this so the scope could still fit in its case with the eaf attached. 
 

BC1DB13B-9A6B-4677-A80C-DA25F9015B8F.jpeg


Edited by Cometeer, 25 November 2020 - 08:03 PM.

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#250 kel123

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Posted 25 November 2020 - 11:09 PM

Someone had asked me for this a while ago, but I couldn’t find who it was. Anyway, here’s the ZWO EAF attached to the Sharpstar with a belt drive. No real advantage of this over the shaft coupler; I did this so the scope could still fit in its case with the eaf attached.

BC1DB13B-9A6B-4677-A80C-DA25F9015B8F.jpeg


It makes the setup look a little bit more complex. It seems like I can see an Askar clamp there.


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