Twin cannons and a bino-viewer

[RobertI]

Feeling more energetic tonight I got out the 102EDR and C8 side by side. My main goal was to see whether the C8 and bino-viewers worked for DSOs. The BV setup in the C8 gave a magnification of around 120x which was a bit high, but I gave it a go anyway.

First was the Trapezium - I was really pleased to see that the E component was immediately and easily visible and the F component was also soon obvious, both with direct vision. The BV worked really well for this. Following on from last night I thought I would try M35 to M38 and was not disappointed, the BV setup worked really well, framing each cluster nicely and encouraging nice long examination. When I viewed M38 I suddenly saw the starfish shape, really striking. It obviously needs a decent aperture to really bring this out. I was so impressed I even made a sketch! See end of post.

Then onto the Eskimo Nebula in Gemini. This was really spectacular and the BV and high power worked superbly on this.

Then onto some galaxies in Leo. M105 and NGC3384 were both visible in the FOV but the third companion NGC3389 could not be seen. Scanning down the bright M96 and slightly dimmer M96 were also easily seen. M65 and M66 were lovely to see in the same FOV but the third member NGC3628 was not found. Switching to a mono eyepiece at 100x I could immediately make out third member, so now I knew where it was I tried the BVs again and could just about make it out. I think the higher magnification of the BV was too much for this fainter galaxy. 

Finally I tried the beautiful double Algeiba in Leo. The colours and brightness through the BVs was mesmerising. I compared the view with the refractor, and although the view through the refractor was cleaner and sharper, I preferred the BV view in the C8 as the stars were so much brighter and more colourful.

So all in all I think using BVs in the C8 for deep sky viewing worked really well, particularly for clusters, doubles and small bright planetaries. The main downside is the high magnification. I could probably get this down to 100x with a 24mm 68 degree eyepiece - unfortunately using the reducer will not allow me to reach focus. But for small DSO the setup worked really well.   

This is the sketch of M38 - it’s not good but I’ve outlined the Starfish shape, which is not clear in the sketch unfortunately, but very clear at the eyepiece. What makes it look like a starfish? Well five legs, but also lots of pair of stars along the length of the legs giving the impression of little ‘suckers’, for me at least. Has anyone else seen the starfish before?

Edited February 27, 2022 by RobertI

[Space Hopper]

Hi.

Would an 'Alan Gee' be worth looking into ?

I've used an 8" SCT a good few years ago and was very impressed with the views with the bino but regretfully sold it to fund other things,

and i've often thought how one of those 'Alan Gee's would have performed with it ?

https://www.firstlightoptics.com/reducersflatteners/baader-universal-alan-gee-ii-telecompressor-uag-ii.html

[RobertI]

On 27/02/2022 at 07:23, Space Hopper said:

Hi.

Would an 'Alan Gee' be worth looking into ?

I've used an 8" SCT a good few years ago and was very impressed with the views with the bino but regretfully sold it to fund other things,

and i've often thought how one of those 'Alan Gee's would have performed with it ?

https://www.firstlightoptics.com/reducersflatteners/baader-universal-alan-gee-ii-telecompressor-uag-ii.html

Thanks for the link @Space Hopper. I did a bit of research on the Universal Alan Gee, and it does look promising, but during my wanderings I discovered that I might reach focus with with BVs and 0.63 reducer if I put the reducer AFTER the diagonal, ie: between the diagonal and the BV. After finding the relevant adaptors, I tried it out and it worked! This gives a magnification of around 70x and a field of view of 0.9 degrees.  Not exactly wide field but not too bad for binoviewing in an SCT. However there were two problems evident when I tried it out: 1) vignetting and 2) distortion toward the edge of field of view which I think is astigmatism (diamond shaped stars). The first problem is due to the very long light path of the binoviewers I believe, and I’m not sure of the cause of the second.

I need to try this combo out under a proper dark sky so might have to wait a few weeks. It will be interesting to compare this view with an unvignetted, undistorted mono view and see which I prefer.