RASA 8 - dew shield vignetting?

[clarkpm4242]

Hi all

I have the standard AstroZap flexible shield on my RASA.  I will be checking the next clear spell however, has anyone noticed vignetting due to the shield length and fast scope?  Thanks, Paul.

@tomato @gorann @ollypenrice

[ollypenrice]

5 minutes ago, clarkpm4242 said:

Hi all

I have the standard AstroZap flexible shield on my RASA.  I will be checking the next clear spell however, has anyone noticed vignetting due to the shield length and fast scope?  Thanks, Paul.

@tomato @gorann @ollypenrice

I don't think it's a good idea to use a dewshiled higher than the back of the camera on this scope. At least, it isn't necessary, since the camera's heat and fanning of the air seems to kill dew easily. You need the camera to be able to vent fully, too, so I made mine end at the back of the camera.

Olly

[tomato]

I have the Celestron dewshield and do experience problems on mild nights with the camera cooling due to re-circulation of the warm fan exhaust air within the confines of the dewshield. My rig is inside a dome so I don't need it for dew protection, but all of the electronics that control the dome has a plethora of LEDS and there are positional lasers in there also so the I need the shield to keep out the stray light.

[gorann]

I have been using the full length of the AstroZap on my RASAs. I do not like the thought of cutting such an expesive item in half - but thinking about it maybe I could get two shields from one:-). I cannot imagine that it would create any reduction in light reaching the scope (you still only have a ca 3° FOV so how could that happen?). In any case it would not cause vignetting - that happens close to the camera. However. I had not thought about the camera-cooling issue, maybe becasue virtually all of my imaging is done below 10°C ambient temperature❄️.

[kirkster501]

Remember that when you use a dew shield you should also leave the shield exactly as is for the flats as well.