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Edge 11 dovetail on top for adding weight-balance and for guide scope? RA finders?

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#26 MikeMiller

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Posted 12 September 2019 - 01:46 PM

So you swap back and forth from the telrad to the guidescope i take it?

 

Now that I do plate solving, the telrad only goes on for visual. smile.gif

 

I don't have experience with the cheap finder scopes modded to be guide scopes, so I can't help there. I would worry about the plastic-looking thumbscrews on the one you linked. I am not a fan of the rings with the clamps like this, as they leave room for vibrations. However, lots of people use them, so I can't help on if it is appropriate.

 

The one I use is a MiniBorg with tube clamps, and an ADM mini-max for aiming. But I rarely need to bother with the mini-max, as the LodestarX2 is sensitive enough with a 50mm guidescope that its rare I don't find a star to guide on.


Edited by MikeMiller, 12 September 2019 - 01:47 PM.


#27 markm75c

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Posted 12 September 2019 - 02:20 PM

Now that I do plate solving, the telrad only goes on for visual. smile.gif

 

I don't have experience with the cheap finder scopes modded to be guide scopes, so I can't help there. I would worry about the plastic-looking thumbscrews on the one you linked. I am not a fan of the rings with the clamps like this, as they leave room for vibrations. However, lots of people use them, so I can't help on if it is appropriate.

 

The one I use is a MiniBorg with tube clamps, and an ADM mini-max for aiming. But I rarely need to bother with the mini-max, as the LodestarX2 is sensitive enough with a 50mm guidescope that its rare I don't find a star to guide on.

I updated my link previously, not that finder per say, but the svbony sv106 60mm is what others on here said works fine and is just a clone of the orion i think.  This one has metal screws:

https://www.amazon.c...sk_ql_qh_dp_hza

 

I think that coupled with this adm adapter on my edge 11's cge dovetail d series bar and i should be ok, unless of course there is too much flexture, i guess ill be able to tell when I test it with the asi290mm mini (i think attaches somehow via 1.25).



#28 MikeMiller

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Posted 12 September 2019 - 04:38 PM

Oh, a helical focuser, nice. That should work well.
 

The losmandy clamps will work great for this purpose. Another advantage is you can clamp other things to it depending on what you are doing. What a widefield camera? Use a losmandy clamp. Telrad/Rigel Quickfinder? Clamp it right on. 

 

I also have my Pegasus Powerbox and other accessories mounted on a small Losmandy dovetail and clamped on to the OTA.



#29 kingjamez

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Posted 12 September 2019 - 04:46 PM

I have the svbony 60mm guidescope with helical focuser. I love the focuser, hate the scope. The stars are badly out of round with what looks like astigmatism. The stars are so misshapen that I’ve never been able to guide well with it. Poor seeing is amplified when the stars aren’t round.

I won’t even sell the guidescope because it’s so bad.

-Jim

#30 markm75c

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Posted 12 September 2019 - 05:30 PM

I have the svbony 60mm guidescope with helical focuser. I love the focuser, hate the scope. The stars are badly out of round with what looks like astigmatism. The stars are so misshapen that I’ve never been able to guide well with it. Poor seeing is amplified when the stars aren’t round.

I won’t even sell the guidescope because it’s so bad.

-Jim

Ah maybe not so good then. I may cancel that order.

Any alternative budget suggestions? What are you using

I think some said this one worked well but it's 135 https://agenaastro.c...cuser-60mm.html

Also the zwo but some said because it rotates coukd be an issue. For now I'll remove the 290 mini and use as oag as well when not doing hyperstar but for f7.

Edited by markm75c, 12 September 2019 - 06:16 PM.


#31 freestar8n

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Posted 12 September 2019 - 05:56 PM

I have been a strong proponent of oag for years - particularly with sct's - but the appearance of low read noise cmos cameras makes guidescopes much more viable because the exposures can be much shorter.  But for that I recommend a good and lightweight guidescope combined with a very small pixel guide camera.

 

A lightweight 50 or 60mm guidescope shouldn't require a dovetail - and if you mount it directly to the OTA on top it will help match any flexure of the OTA with the guidescope.

 

For years people claimed oag had no benefit over guidescopes because centroid accuracy is 1/30th of a pixel or something.  That was a general claim and to me it was ridiculous.  Even 1/10th of a pixel isn't generally true because so many factors are involved.

 

But in my case with EdgeHD11, on a good night I can get below 1.5" fwhm with OAG, but I don't think I can get much below 2.5" fwhm with a 60mm guidescope.  But many people would be happy with round, 2.5" stars - and I think it's possible with 2-4m exposures with sct.  But 10-20m exposures are not likely to do well.

 

The best small guidescope I know of is the Baader VarioGuider - which includes a very good bracket.  It isn't as sharp as I would like - but it is much sharper than the inexpensive ones with a helical focuser.  There may be mixed batches of those and some of them are ok - but the one I have is unusable.  The Baader shows some flaring - but the resulting guidestars have about 4" fwhm when tightly focused on a 290 sensor.  And that should provide a reasonable guide centroid.

 

You do need to polar align well when using a guidescope - and keep the exposures relatively short.  OAG is definitely the way to go if you want max detail.  But a lightweight but high quality guidescope combined with small pixels and short exposures can do well and is easier to set up.

 

Frank


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#32 kingjamez

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Posted 12 September 2019 - 06:36 PM

Ah maybe not so good then. I may cancel that order.

Any alternative budget suggestions? What are you using

I think some said this one worked well but it's 135 https://agenaastro.c...cuser-60mm.html

Also the zwo but some said because it rotates coukd be an issue. For now I'll remove the 290 mini and use as oag as well when not doing hyperstar but for f7.

I use a 290mm-mini with a Nikkor 180mm F/2.8 lens as my guide scope. I use it at F/4. I taped the focus ring to keep it at infinity focus and use a baader helical focuser to fine tune. I bought the lens on eBay not in perfect condition for $150.

I use a green filter to kill any chromatic abberation. I don't know if this helps but I get really sharp round stars with PHD reported HFR's of 2.0-2.3 (IIRC FWHM is reported at 1.0 but I'm not as certain about this). The star profile has steep walls. This is all predicated of course on having good seeing. It happened for me 2 nights ago and man is everything easier when seeing is good.

Edited by kingjamez, 12 September 2019 - 06:38 PM.

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#33 markm75c

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Posted 12 September 2019 - 10:39 PM

I pretty much have settled on the ~240mm FL 60mm agena astro i linked above at this point.  Seems it has a non rotating focuser.  I know i've set the bar low budget wise, but it sounds like there is success there as well ($80-$150 vs say $350+).

 

One odd note, i think i've seen it referenced that this "short tube celestron 70mm with fl 400" seems to have been used for general (f7) guiding by some with an edge 11, i think.

i already have the oag coming, however, it would have been interesting to have a higher FL refractor like this to test and do a compare at F7 with phd2 values vs the oag (both 290mm mini).

https://www.amazon.c...sk_ql_qh_dp_hza

 

Its only $72, i might just get it as well then compare both guidescopes laugh.gif  Not sure if the bar under this scope is the same size as the one on the agena, to just fit in the adm clamp i have coming.

 

I'm not sure how much trouble ill run into with taking the asi290 mini in and out of the guidescope and moving it to the oag and back and forth.  If this becomes a pain each time then (assuming it works well with oag and i dont need a 174mini) i'd probably buy another asi290 mini so it doesnt need removed to use one or the other. 

Does anyone do this, share a camera between oag and guidescope (probably only if you do hyperstar i'd guess on the 11 anyway)?


Edited by markm75c, 12 September 2019 - 10:41 PM.


#34 markm75c

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Posted 12 September 2019 - 10:44 PM

I have been a strong proponent of oag for years - particularly with sct's - but the appearance of low read noise cmos cameras makes guidescopes much more viable because the exposures can be much shorter.  But for that I recommend a good and lightweight guidescope combined with a very small pixel guide camera.

 

A lightweight 50 or 60mm guidescope shouldn't require a dovetail - and if you mount it directly to the OTA on top it will help match any flexure of the OTA with the guidescope.

 

For years people claimed oag had no benefit over guidescopes because centroid accuracy is 1/30th of a pixel or something.  That was a general claim and to me it was ridiculous.  Even 1/10th of a pixel isn't generally true because so many factors are involved.

 

But in my case with EdgeHD11, on a good night I can get below 1.5" fwhm with OAG, but I don't think I can get much below 2.5" fwhm with a 60mm guidescope.  But many people would be happy with round, 2.5" stars - and I think it's possible with 2-4m exposures with sct.  But 10-20m exposures are not likely to do well.

 

The best small guidescope I know of is the Baader VarioGuider - which includes a very good bracket.  It isn't as sharp as I would like - but it is much sharper than the inexpensive ones with a helical focuser.  There may be mixed batches of those and some of them are ok - but the one I have is unusable.  The Baader shows some flaring - but the resulting guidestars have about 4" fwhm when tightly focused on a 290 sensor.  And that should provide a reasonable guide centroid.

 

You do need to polar align well when using a guidescope - and keep the exposures relatively short.  OAG is definitely the way to go if you want max detail.  But a lightweight but high quality guidescope combined with small pixels and short exposures can do well and is easier to set up.

 

Frank

What guide scope are you using in your case, is it the 85mm in your sig? Or some other 60mm variant?

The baader you mentioned sounds a bit out of my price range (i think $400 +)

 

I would think for real guiding (not for hyperstar like my case), something with a FL of 400+ at f7 minimum would be needed to even get decent values?  (hence my last post I mentioned there is a cheap celestron 70mm at 400mm FL that looked like an interesting test case at least for stat testing, but i'm sold on doing oag for f7/f11



#35 kingjamez

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Posted 12 September 2019 - 11:10 PM

 

Does anyone do this, share a camera between oag and guidescope (probably only if you do hyperstar i'd guess on the 11 anyway)?

Yes, I do it but if there weren't a hundred other things I want to buy, I'd have a second guide camera.

 

I have a 3D printer and can make custom spacers. I measure where the 290mm fits in the focuser for best focus and make a custom spacer so it goes back to the same spot each time. 

 

-jim


Edited by kingjamez, 12 September 2019 - 11:11 PM.


#36 freestar8n

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Posted 12 September 2019 - 11:21 PM

What guide scope are you using in your case, is it the 85mm in your sig? Or some other 60mm variant?

The baader you mentioned sounds a bit out of my price range (i think $400 +)

 

I would think for real guiding (not for hyperstar like my case), something with a FL of 400+ at f7 minimum would be needed to even get decent values?  (hence my last post I mentioned there is a cheap celestron 70mm at 400mm FL that looked like an interesting test case at least for stat testing, but i'm sold on doing oag for f7/f11

It is a fairly small 60mm f/4 guidescope with a decent but not perfect lens and a very good bracket.  But it isn't inexpensive:

 

https://optcorp.com/...der-bracket-kit

 

With a 290 guide camera this yields 2.4" per pixel.  If the stars are tight enough to span 2-3 pixels, this can give you a fairly well sampled 4" or so fwhm guidestar - and the centroid accuracy should be pretty good - but not as good as with oag and a tight guidestar.  Some people guide oag with big oddly stretched stars because there is still a centroid to guide on.  But I view the size and shape of the star spot as important for good centroid accuracy.   The recent cmos sensors with very small pixels and low read noise have mad small guidescopes much more effective - and when you combine that with imaging sensors that don't need long exposures - it's a win-win.

 

In the past, with 7.5um pixels or so - you would need a longer and heavier guidescope for decent centroid accuracy - but not with 2.9um pixels.

 

As for the oag sensor - the 290 would work fine as long as you find a guidestar - but the 174 is much larger and as long as you have a decent size oag prism - and the sensor isn't far from the prism - the 174 should have a much wider field and make it easier to find guidestars.  So I recommend the 290 for guidescope - and 174 for oag.  And for oag the guide sensor should be 1.25" so it can slide into the guide port and get close to the prism.

 

Having the oag set up properly with a good prism and sensor makes a huge difference in how easy it is to find guidestars - and the quality of the guiding.

 

Frank



#37 markm75c

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Posted 13 September 2019 - 09:18 AM

I'm curious.. Does anyone know if this orion 80st is the same as the orion st80 that many use as a guide scope? (or which model they are buying if new?)

https://www.amazon.c...e/dp/B0732VG4ZP

 

That price like with that celestron short tube 70mm on amazon, seems crazy (add rings though).



#38 MikeMiller

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Posted 13 September 2019 - 02:59 PM

Does anyone do this, share a camera between oag and guidescope (probably only if you do hyperstar i'd guess on the 11 anyway)?


Yes, I do this for the LodestarX2. But if I was buying a new guidecam today, I would get an ASI290 or some other CMOS cam.

In fact I have a 290, though I don't use it for guiding since I have the Lodestar.

For guiding it's all about reducing flexure. My setup might be overkill, but if it's worth killing, it's worth overkilling.

#39 markm75c

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Posted 13 September 2019 - 07:19 PM

I have the svbony 60mm guidescope with helical focuser. I love the focuser, hate the scope. The stars are badly out of round with what looks like astigmatism. The stars are so misshapen that I’ve never been able to guide well with it. Poor seeing is amplified when the stars aren’t round.

I won’t even sell the guidescope because it’s so bad.

-Jim


I've just come across some in the hyperstar group that use the svbony. They said the front lens is installed backwards and causes distortions n halos. They turned it around and no issues did you try this before. I'm curios

#40 kingjamez

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Posted 13 September 2019 - 08:07 PM

I've just come across some in the hyperstar group that use the svbony. They said the front lens is installed backwards and causes distortions n halos. They turned it around and no issues did you try this before. I'm curios

Unfortunately yes. I had dramatic halos that appeared when I reversed the lens. I read a similar report and high hopes for that working.

It wouldn’t surprise me if there is dramatic variation in these guide scopes. I believe it if folks say they are good, I just know that my particular example is dramatically bad.

-Jim

Edited by kingjamez, 13 September 2019 - 08:08 PM.


#41 montejw360

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Posted 14 September 2019 - 11:56 AM

I wanted to jump back to my question here. Can anyone point out why I would choose one of these over the other. I'll either have a 60 or 80mm guidescope on top plus I just bought the ADM d series weights though those will hopefully fit on the lower plate but I think if not they need the cge plates width. So I guess the choice is cge here?

 

The ADM option I think is vixen size. 

Celestron also makes a narrow Vixen size dovetail for the 11" EdgeHD sct.

 

https://www.celestro...a430f4d47&_ss=r


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#42 kingjamez

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Posted 16 September 2019 - 09:24 PM

I use a 290mm-mini with a Nikkor 180mm F/2.8 lens as my guide scope. I use it at F/4. I taped the focus ring to keep it at infinity focus and use a baader helical focuser to fine tune. I bought the lens on eBay not in perfect condition for $150.

I use a green filter to kill any chromatic abberation. I don't know if this helps but I get really sharp round stars with PHD reported HFR's of 2.0-2.3 (IIRC FWHM is reported at 1.0 but I'm not as certain about this). The star profile has steep walls. This is all predicated of course on having good seeing. It happened for me 2 nights ago and man is everything easier when seeing is good.Just a

Just as a follow up to this post. I got a chance to take a screen grab of my star profile using my 180mm prime camera lens. This is what I shoot for when guiding, nice round stars. I wish I could say authoritatively if it made a difference, but due to the nature of guiding and it's variability seemingly minute to minute, I cant... that said I "feel" like I get better guiding for whatever that's worth.

 

-Jim

Attached Thumbnails

  • PHD_Star.jpg


#43 markm75c

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Posted 18 September 2019 - 10:56 PM

I've been testing the sbvony 60mm, so far i think its ok, but i'm not 100% positive. I've not done alot with star fields to know how well it + the asi290mm are fairing or if my settings are dialing it in for this test, well enough.

Here are some shots (i've not flipped the lens around, but i've had to pretty much extend the guidescope + cam all the way out)
 
 guidescopecap.JPG
 
guidescopecap2.JPG

guidescopecap3.JPG


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