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Author Topic: QHY miniguidescope on EdgeHD 8"  (Read 1159 times)

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Offline souls33k3r

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QHY miniguidescope on EdgeHD 8"
« on: 18:20:37, 15 September, 2016 »
Hi All,

Been thinking of getting in to Astro imaging for a little while now but finally i've got my act together and have decided to go for it.

Previously i was hoping to get a start with CCD but then the prices shot up so going to end up imaging with a DSLR (for now).

My scope is a EdgeHD 8" and the mount is NEQ6 Pro. Going to be buying a reducer to bring the FL down to 1422mm at F/7 so here's to me hoping for the best  :urock:

Initially i've been thinking of going towards the OAG route but have decided against it only because the amount of trouble one could have finding a guide star is going to be nothing but painful and where i live, it's crazy light pollution as well so decided to go down the Guide Scope route.

Yesterday i called in Modern Astronomy and spoken to Bern (an absolute gem of a person) regarding pole master so thought i should ask if he does any variation of a 80mm guidescope.

What he suggested was to forget about the 80mm guide scope and go with the lighter QHY miniGuidescope route. Yes it has a small aperture and short focal length but he said i don't really need anything bigger than. He said he has tested this and can highly recommend this little thing.

http://www.modernastronomy.com/shop/accessories/qhy-accessories/qhy-miniguidescope-kit/

I have not been able to find much in the internet on this so thought i should ask here what you experience people have to say about it.

I did tell him the FL i will be working on is going to be 1422mm and he said if i couple my mount with Polemaster, i can go even higher on the FL with that. Also achieving more than 5 minutes is going to be not a problem, 10 quite possible and he knows of someone who has used it at 15 min exposures as well.

The calculations on http://www.wilmslowastro.com/tips/autoguiding.htm makes sense, and what Bern said that i should forget about lodestar x2 as a guidecamera and use the QHY5L-ii instead because it has smaller pixels and will marry in just perfectly with this miniGuidescope kit.

Thanks in advance

Offline PaulB

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Re: QHY miniguidescope on EdgeHD 8"
« Reply #1 on: 19:08:51, 15 September, 2016 »
I think you've got everything needed to get you up and running.
The Edge is a very good telescope. And the QHY guidescope kit, will be more than suitable.  Bern is right about the camera choice to. I use a QHy5L-II mono camera for guiding, using a 50mm lens. Guide stars are very easy to locate and lock onto.

Couple the mount up with a QHY pole master. And you should have plenty of imaging fun.

I use a C9.25 with a modded Canon 1000D for Deep sky imaging. It works very well.
Paul.
"Whirlpool Observatory"
Losmandy G11-Gemini L4.
Celestron C9.25.
Megrez 80 ED II Triplet.
Orion OMC 140
Altair 115ED F7
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Offline chris.bailey

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Re: QHY miniguidescope on EdgeHD 8"
« Reply #2 on: 20:06:34, 15 September, 2016 »
Not often I would disagree with Bern but personally I would not use anything but an OAG on a scope of over 1000mm focal length. I tried a guide scope with my 10" RC (2m, f/8) and the results were not pretty!

1) Differential flexure is very real, however solidly you think things are fixed down, they do move. At a focal length of 2m or even 1.5m with a focal reducer, your image scale is such that very small movements in one or the other have an impact. 1 arc second is an unbelievably small angle but that is what you are talking of being in control of. I have had long discussions on another forum with a guide scope user who tried everything to tame guiding on a 140mm frac, including some very expensive scope rings. He eventually tried an OAG and solved them all at a stroke.

2) The image scale difference between guider and imager is going to be significant, probably in the order of 8:1, maybe even more. So you do really well in getting the guide corrections to within 0.25 arc seconds (and that is superb guiding, expect twice that) you are making corrections of 2 arc seconds at the imager scale. If you are imaging at 1 arc second per pixel thats 2 pixels at the imager end of things. Thats quite a lot.

3) Good guiding is reliant on having a reasonable guide star signal to noise ratio. The Lodestar II is a LOT more sensitive than the QHY. With an OAG/Lodestar I have only once had issues with getting a decent guide star and thats M51, which is well known as being devoid of nearby stars.

Now I know of a few people who do just what you are talking about in using a guide scope so by all means give it a try. My money would be on you finding it problematic.

Just my 2p'th

Chris
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Offline souls33k3r

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Re: QHY miniguidescope on EdgeHD 8"
« Reply #3 on: 09:44:22, 16 September, 2016 »
I can totally agree on using OAG but someone who has absolutely no experience in using one and to hear it from most of the people how NOT easy it is to use one, i really am on the edge. My heart says go with the OAG, but my mind says "Stick to the easy option" ... i live in London and the light pollution is crazy, not sure how much an OAG will be helpful in such conditions.

Offline ChrisLX200

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Re: QHY miniguidescope on EdgeHD 8"
« Reply #4 on: 10:04:22, 16 September, 2016 »
Certainly an OAG is the better option for any SCT - as is the addition of a secondary focuser so you can lock the primary and forget moving it to achieve focus. I think with an OAG it's mainly the initial setup which is problematic, having to achieve good focus with two cameras at once sounds very tricky but it's not actually difficult - just fiddly. However, once done you don't have to do it again and you're ready to guide whenever the main scope is focused.

For a guide camera I believe the Altair offering based on the Aptina AR0130 CMOS sensor is sensitive enough to work very well in an OAG and much cheaper than the X2. The QHY5L-IIM with the MT9M034M sensor isn't bad either but given a choice I would go with the Altair camera.

It really depends how critical you're going to be of your results, stars that are a little 'eggy' may not bother you much at first but eventually they will start to annoy the heck out of you! An SCT is a difficult beast to master for astro-imaging.

ChrisH
Chris Heapy - current: 10-Micron GM2000HPS-II U/P, G11/Gemini, TV NP127is, Altair 8" RC, TV Genesis SDF, TV Pronto, SW Equinox 80ED, 10" LX200, 12" f/5.4 Newt, Vixen 90mm.
Atik 490EX, Atik EFW, Baader LRGB filters, Astrodon 3nM NB filters, Lodestar, QHY5L-II all-sky, Canon 70D and 350D
Whirley Obs., MPC Code Z89

Offline souls33k3r

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Re: QHY miniguidescope on EdgeHD 8"
« Reply #5 on: 10:28:11, 16 September, 2016 »
Not moving away from the topic but am wondering if i do choose to go down the OAG route:

1) How easy/difficult will it be to find a guide star if i choose to use a lodestar x2 or any other super sensitive guide cam in a heavy light polluted area? I live in London.

2) What is the maximum exposure i should expect before light pollution kicks in?

Offline PaulB

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Re: QHY miniguidescope on EdgeHD 8"
« Reply #6 on: 10:46:01, 16 September, 2016 »
I found using oag a real pain in the butt.
I use a Qhy5l with a cheap 50mm lens and also a 50mm guidescope. The GS is mounted to my C9.25. I have never had any problems with flexibility. I can happily guide and take 900 second subs, and see tight round stars.
Paul.
"Whirlpool Observatory"
Losmandy G11-Gemini L4.
Celestron C9.25.
Megrez 80 ED II Triplet.
Orion OMC 140
Altair 115ED F7
Coronado PST
Atik 428EX
Atik EFW 2
QHY5L-II.
Modded Canon 1000D.
IOptron Mini Tower II
CCD Images
http://www.flickr.com/photos/paulabrierley/

Offline souls33k3r

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Re: QHY miniguidescope on EdgeHD 8"
« Reply #7 on: 11:19:11, 16 September, 2016 »
Paul, how have you got the 50mm guidescope mounted on your SCT? Got any images to share to show what your set up looks like? Ta

Offline Einari

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Re: QHY miniguidescope on EdgeHD 8"
« Reply #8 on: 13:46:27, 16 September, 2016 »
I guess in London you should use narrowband filters or at least uhc filter.
Others can surely tell what exposures you can use there.
I'm one of those who have never used oag with SC scope - and not having any flexure problems as far as I can tell. And now use just normal finder guider setup.
Tapio

Celestron C8, C9.25" & Hyperstar, iOptron CEM60-EC, TS 80 triplet,  Coronado PST, SXV-694,  ASI120MM/ASI174MC Cool

 

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