Saturn, 15th July

[Tommohawk]

Met up with some Astro chums at a local dark sky site - don't really need this for Saturn of course, but  this site has great views to the horizon, unlike my garden. Nice also to meet up with folk and be able to natter about Astro stuff especially as it saves boring the pants off of family members

Unfortunately the haze low down was pretty obvious, and just got worse as the night went on. So again I gave up on longitudinal detail and just lumped all the AVIs together and stacked them without taking account of rotation.

Quattro 10S with Powermate x5, ASI290MM + RGB, 8 x 60 sec AVIs for each of RGB, R as LUM.  About 38000 frames for R, and bit less for G and B. PIPP best 50%, AS!2 best 30%, and for a change I did all the sharpening in PS rather than Registax. I can see what I'm doing better in PS, although colour balance becomes a bit weird. Hope you like it, happy to receive and comment/criticism!

 

[si@nite]

Looks great to me, nicely done!

[Pete Presland]

Doesn't look too bad despite the problems you had. I would still expect to se some banding, even with rotation.

[morimarty]

Great image scale Tom. It looks good.

[Tommohawk]

Thanks folks. This year I've been experimenting with the Quattro for planetary. Obviously not really the tool for the job, but with a 5x powermate the image scale is about right - probably oversampled for the conditions. Trouble is I'm comparing my results to Jupiter and Saturn last year, when the elevation was that much higher.

Its interesting that although the Quattro has a large secondary as its mainly for DSO/ widerfield stuff, the secondary is only 82mm (30.5%) compared to the C9.25 - generally regarded as the "right scope" for planetary - which is 85mm. (35%)

If there is a glut of clear sky (and time) I might experiment with some artificial central obstructions of various diameters just to see what the effect is. The experts do seem do differ somewhat in their opinions on CO, so would be interesting to do some real world experimentation.

I think longer term I'm heading for a larger aperture Do, maybe 300mm, for planetary with a custom small secondary. Having "done the math/s", if only using the Dob for planetary where a small fully illuminated field is required, a CO of only 20% is easy to achieve esp because with the ASI cameras the back focus is so short. 

 

[morimarty]

Hi Tom. I did some visual experimenting of the CO with an orion optics 10"F4.3 some years ago which as a 63mm secondary. I replaced it with a 50mm secondary and the results was startling there was definitely more contrast on jupiter visually. So reducing the CO will certainly improve contrast you could even try flocking the tube some people swear by it. But in general with todays software I think you can negate any gains made.  JIMO?

[orion25]

Awesome results especially considering the conditions. Great image scale and ring detail!

Reggie

[Tommohawk]

On ‎20‎/‎07‎/‎2018 at 11:18, morimarty said:

Hi Tom. I did some visual experimenting of the CO with an orion optics 10"F4.3 some years ago which as a 63mm secondary. I replaced it with a 50mm secondary and the results was startling there was definitely more contrast on jupiter visually. So reducing the CO will certainly improve contrast you could even try flocking the tube some people swear by it. But in general with todays software I think you can negate any gains made.  JIMO?

Thanks, that's interesting. Most of my first planetary was done with a SW 200P, not the PDS, and this seemed to give exceptional results given the modest aperture - presumably partly because of the smaller secondary. (52mm vs 58mm)

I thought about swapping out the Quattro secondary for a smaller one when doing planetary, but I think it would be difficult to maintain collimation. That said, because the Quattro is a bit of a beast to collimate, its probably simpler  just to go with a different slower scope.