Although I can achieve focus with my HD1100 with the OAG, Optec focuser, EFW, and focal reducer, I am still struggling to get the guide camera focused! The backup is a 400 mm lens used as the guide scope, which works quite well.
Peter
In a message dated 4/22/2020 2:15:18 PM Pacific Standard Time, forums@mainsequencesoftware.com writes:
Hello Farzad,
Please see some screenshots from my setup. Hope this is helpful.
Telescope: Celestron Edge HD 8 w/ 0.7x reducer
Focuser: Celestron Motorized focuser
Camera: ASI1600MM Cooled, 8-position EFW, ASI120MM (guide camera)
SGPro, pHD2, Pegasus powerbox, PoleMaster
Any other questions are most welcome!
With kind regards,
David Fielder
**Fielder Scientific Consulting **
I have a Moonlite too with my C8 Edge HD. and it works very nice. The advantage is that yon can insert the reducer for about 2/3 of its lenght inside the focuser.
JM
The backfocus is 105 mm behing the reducer x0.7 or 133 mm behind the scope without reducer for the C8 Edge HD and I am using a Orion thin OAG too. It is only 10.5 mm thick.
JM…
Thank you for sharing. I have nearly identical setup except I use the C8 at F10. I have tried many different combinations of setups and still could not make it work as well as yours, which seems to have doughnut shape stars too, and I think someone said that could be a challenge to SGP.
A replacement focus motor is on its way. I will report back.
Farzad
I agree with you. It seems like a lot of trouble using OAG but the parallel guiding has its own issues too. I have a lot of rings for my C8 and one that I designed and fabricated online so I could use the OAG with the reducer.
You’re most welcome Farzad,
The donuts you see are from the last focusing at maximum defocus to show you SGPro running the V curve calculations.
Attached are two single images after refocusing at minimum HFR, which is typically 1.2-2 for in the city. I’m quite pleased with the sharpness of the stars. The zoom is 3x of full.
Seeing 2 nights ago was not great with my phD2 RMS running about 1-1.2 arc-sec. Typically for my setup in the city on a good night, the RMS is closer to 0.5 arc-sec.
I have a HOTEC 3-laser collimator which I use once a year to ensure collimation is optimum.
Hope your new focuser performs better than your first one.
David
Hi David Fielder,
We have the same set-up and I would be interested to know what your backlash setting is for the Edge HD? Mine is set at 2000. I’ve struggled with this focuser so I set the backlash deliberately high in order, hopefully, to take it out of the equation.
Robin
I am looking into the CHL focuser as well. It looks really good. And I have a mini controller from them already. I will have to get a thinner OAG or just get a parallel guiding setup.
I just purchased a Moonlite CHL 2.5 specifically foy my C8HD. Not had the time to test it yet - no good conditions at present. Setting it up is quite straightforward and leaves a great feeling of quality.
The problem I’m facing is more with guiding. OAG at this focal length works well when you find a guide star in the tiny field, but when flipping at meridian is always a bet. I ruined several nights because of this problem.
Parallel guiding is an option I implemented years ago but has other challenges: focal length needed, hence weight, hence potential differential flexure…
Congrats on the CHL2.5. What did it cost? The website doesn’t say.
A great advantage of an OAG is that it it compatible with the main scope and it also does not need a dew heater. Imagine if the guide scope dew heater went bad in the middle of the night.
Meridian flip is a challenge, I am always awake for it and attending the event any way. My biggest fear is not being able to center after a flip. For guiding, technically the prism should be picking back up in the same corer of the sky as it was doing before. And one thing I constantly have to remind myself is that there will be more stars visible in the dark sites when I do my real imaging than when I practice from in between trees out of my house.
I have not done this for almost a year now any way. A parallel guide scope would be a good backup.
Farzad
Unless you rotate the camera 180 degrees then it would actually be 180 degrees from where you were before.
Jared
I stand corrected. I remember now that post-flip images are rotated 180 degrees. And in fact it helps me remember back when I strategist this I imagined including this effect as part of initial composition, so that we know stars will be available in the other corner.
The CHL plus the stepper motor incl. controler takes you to about $ 900. Not cheap indeed, but quality is there,
As indicated by Jared in a later response, meridian flip turns everything 180°, meaning that the guide star is lost; you would cross your fingers that the guide camera is able to pick one up. In some areas of the sky, this is really a challenge.
CS
Rodolphe
That looks expensive. But I won’t be needing the controller part of it.
Sure it is. But quality is there, I can assure you.
