Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

Help deciding on an OTA

hemmi

By hemmi
in EEVA - Reports

Recommended Posts

hemmi

hemmi

Posted
Posted

My goto Dob is great for visual and ok for short exposure shots of the bright stuff, but decided I needed something better.   A year ago I sold my CG-5 & Astrotech AT72ED, and have missed it since.  I have been looking at getting a LX200 but the weight and portability changed my mind.

So I bought a Celestron Advanced VX mount to replace my sold CG-5.  Now what OTA would be best for this mount.  Here are some of my thoughts:

RC6 Astrotech/GSO/Mallincam - will require focal reduction

8" SCT - Celstron/Meade - will required heavy focal reduction

80mm ED refractor

I'm leaning more toward the RC6 or SCT as I want to do some visual and/or planetary imaging.  What are the benefits of the RC vs SCT?  as the focal lengths are similar.

Whatever I get will be used with my mallincam Jr. Pro.  Thanks!

Link to comment
Share on other sites
Dwight

Dwight

Posted
Posted

The SCT will have a smaller secondary obstruction than the RC. The RC will have a flatter field but that doesn't come into play using the small chips in astrovideo cameras. Either one can be used well with focal reducers. Kind of a toss up....Dwight

Link to comment
Share on other sites
Astrogate

Astrogate

Posted
Posted

The SCT will have a smaller secondary obstruction than the RC. The RC will have a flatter field but that doesn't come into play using the small chips in astrovideo cameras. Either one can be used well with focal reducers. Kind of a toss up....Dwight

Adding to what Dwight mentioned I would like to say that a very important plus for the RC scope is this scope start out faster at F8 native compared to the F10 native of the SCT. If you main interest is deep sky objects then I would go with the RC scope. I have used my beloved C9.25 SCT for over 10 years and really enjoyed it. I recently obtained a VRC10" scope mainly for the wider corrected flat FOV for my MC Universe CCD camera, but I was stunned by the amazing results with this scope using my MCX2 video camera. The stars were much tighter and the near live images had a more CCD photo quality to them.

Chris A

Astrogate

Link to comment
Share on other sites
hemmi

hemmi

Posted
  • Author
Posted

Adding to what Dwight mentioned I would like to say that a very important plus for the RC scope is this scope start out faster at F8 native compared to the F10 native of the SCT. If you main interest is deep sky objects then I would go with the RC scope. I have used my beloved C9.25 SCT for over 10 years and really enjoyed it. I recently obtained a VRC10" scope mainly for the wider corrected flat FOV for my MC Universe CCD camera, but I was stunned by the amazing results with this scope using my MCX2 video camera. The stars were much tighter and the near live images had a more CCD photo quality to them.

Chris A

Astrogate

What about the contrast?  Does the RC have better contrast due to the flocking?  Or the SCT due to the coatings?  Also is one better than the other for light polluted skies.  Thanks!

Link to comment
Share on other sites
Astrogate

Astrogate

Posted
Posted

What about the contrast?  Does the RC have better contrast due to the flocking?  Or the SCT due to the coatings?  Also is one better than the other for light polluted skies.  Thanks!

Hemmi to be honest I found also not only were the stars much tighter using my VRC10" scope over my C9.25, but the contrast was better and that what gave my observing experience a more CCD photographic look to my near real-time images. The knife edge baffling is really well done and there is no corrector plate to deal with providing excellent contrast. You will get diffraction spikes though on the brightest stars due to the secondary spider veins holding the secondary mirror but I tend to like those spikes. Also there is no image shift what so ever when refocusing or moving across the meridian with the RC scope. Also I do not need to use a dew shield which was an issue on windy nights and on most nights I have no issue with dew formation except when it is extremely humid out. after a couple of hours my secondary mirror will start to dew up, but I have corrected this occasional issue with my so called homemade dew heater. 

Chris A

Link to comment
Share on other sites
Astrogate

Astrogate

Posted
Posted

What about the contrast?  Does the RC have better contrast due to the flocking?  Or the SCT due to the coatings?  Also is one better than the other for light polluted skies.  Thanks!

Both scopes were good under light polluted skies but the knife edge baffling of the RC scope does tend to help by increasing the contrast.

Chris A

Link to comment
Share on other sites
hemmi

hemmi

Posted
  • Author
Posted

Well I decided on the VRC6,  Hope it provides good views.  I will have to save up for a mfr-5.  I have several regular .5x reducers which should get me by at 684mm FL.  This is slightly slower than my 10" dob at 617mm FL with a .5x reducer.  I would like to get it a bit lower, and I think this is possible with the MFR-5, as it says in specs it will go to .3x.  

Can I increase the distance to sensor with a standard .5x reducer to bring it down to say .4x?

Link to comment
Share on other sites
hemmi

hemmi

Posted
  • Author
Posted

Is that the equivalent if the sw heq5..most mounts are sw will be nice to get a review on the new mount..davy

I have not heard any comparisons of the AVX vs HEQ5 yet.  The HEQ5 is superior to the old CG-5 mount, but this AVX is far beefier than the CG-5.  So time will tell, I think most are happy with the AVX so far.  I had a CG-5 that I used for astrophotography with a 72mm ED refactor and it worked great.  I'm sure the AVX will do better with a larger payload, we shall see.

The VRC6 OTA is only 11 pounds, add on a small autoguider and cameras will still be less than 20 pounds.  Maybe a bit much for 10 min subs, but perfectly fine for video.

Time will tell, but I think I will be happy. 

Link to comment
Share on other sites
hemmi

hemmi

Posted
  • Author
Posted

Well the curse set in and the clouds rolled in.  However I was able to video the moon for about 10 min.  I also toot a glimpse at m42 through the clouds before it got too thick.  I did take a few 30-40 min exposures of some random stars just to test tracking.  With my poor 2 min alignment stars were nice and round at 40 sec.  So I'm happy about that.  Looks like the next time I will get to test is at least 2 weeks away :(

FOV with a .5x reducer was pretty good.  The entire moon (plus some) is visible in the FOV

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.