Trying to become friends with the C6

[grjsk]

29. october, 2022: Langhus, Norway (60°N, 11°E) – Bortle 6 

Seeing: Pickering 3-5

Equipment: 72mm doublet and a C6, AZ-GTI on a Leofoto LM-363c tripod, 32mm Celestron Plossl, Baader Mark IV zoom, Nagler 3-6mm zoom

 

The quest this evening was to become friends with my C6. I have never quite gotten it to «work». I purchased it as a lunar and planetary scope, with the assumption that it would significantly outperform my 72mm refractor. IIt has not done so so far. I spent 90 min collimating it the evening before, and it is stored in a shed outside, so temperature and collimation shouldn’t be a problem this time around.

The first warning sign came early. Orions Belt had just risen above the horizon, and they were twinkling like a disco. A quick star test revealed conditions between Pickering 3 and 4. Not good.

I go straight for Jupiter with the 72mm. Rather poor. 2 bands, but not much else. I switch to the C6. Jupiter is brighter, but no more details. I go back and forth for an hour, but the C6 is unable to pull ahead. I was hoping for a slight improvement atleast, even under poor seeing, but no dice.

I move on to Mars, and here the C6 is slightly better. I can spot Terra Sirenum, and a slight darkening all the way to the north. Once seen in the C6, I am able to faintly see it in the refractor as well. Dew has already becoming a problem, and moist in the air is the main culprit this evening. I pack up, still not convinced the C6 is worth it. Sure it was poor seeing this evening, but if the only time it will significantly beat a much smaller refractor is under good conditions, I am not sure I’ll keep it. I have a 90mm refractor on the way, we’ll see how the C6 handles that competition.

 

[RT65CB-SWL]

Is it the C6-N or C6/SCT ?

[grjsk]

SCT

[Elp]

I quite like mine. Looking at the moon looks like you're flying above the surface in a space shuttle. 

Regarding dew, it's a large piece of glass, you need bare minimum a dew shield, the shield will also reduce stray light entering the tube. If you look at any light reflecting off the inside of the OTA, its quite bright and will affect the perceived contrast. Get a dew heater ring and dew won't be a problem at all. 

They do need cooling down to ambient, I don't bother and still get good views.

If your collimation is out, check it with a Duncan mask.

It will never be on par with a refractor due to the central obstruction, but try getting the native focal length and aperture with an equivalent refractor at a similar price.

Edited November 22, 2022 by Elp

[RT65CB-SWL]

As per what @Elp says above.

A dew shield is a must have [a minimum of 1/3rd of the focal length of the OTA is recommended] and so is the cooling down to ambeint. I give my C6/SCT and 're-modded' ETX105 a minimum of thirty minutes and leave the end cap on the visual back/eyepiece port off facing skywards when it is on the mount before I insert an e/p or other accessory.

Edited November 23, 2022 by Philip R