Frustrations

[Averton (P and C)]

It all started around Jupiter being in opposition. We thought that this was supposed to be the ideal time to image the planet, then issues started. First every time we had a cloud free opportunity the seeing was extremely bad. You could see better looking through a kettle of boiling water. This occurred on several occasions. Then came the uncontrolled dew. Several weeks later after making dew shields, dew heaters and insulating everything possible the scope looks like a polar explorer. Finally on two occasions (slow learners) the astro cloud predicting sites showed a cloud free night after a sunny day. So we setup all the gear, went inside to have tea and wait for darkness only to go out to see clouds from horizon to horizon and on the second occasion to find everything wet from light rain!!!! Anyway last week we finally had two nights where we did manage to get a couple of images.


5 inch F5 scope, Prostar C2 camera, 3x barlow with an extension tube making it 3.5x (giving 0.33 arcsec per pixel which is well beyond the Dawe’s limit of 0.89 for a 5” scope), IR pass filter (to combat the bad seeing)


Images without GRS 24/6 one IR pass only other colourised.
Images with GRS 25/6 one IR pass only other colourised also IR image of Saturn.


Peter & Clare

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[Anth10 (Anthony M)]

Well the results shown here must be of some relief. They are very respectable indeed.
Anth

[Averton (P and C)]

Hi Anth,
Thanks. Yes we were very happy to get a couple of images after so many failed attempts.
P&C

[Atmos (Colin)]

You’re picking up some nice details on jupiter in particular

Something worth mentioning is that the Dawes Limit largely refers to point like sources. When looking at features on the moon or planets you can go to about 1/10th of that. If memory serves an 8” telescope under excellent seeing you can detect lunar features down to about 1km which is well beyond the Dawes Limit.

[Averton (P and C)]

Hi Colin,
Thanks for that info. We will try pushing the magnification a bit more on planets and the moon. It is worth a try. See how we go.
Clare & Peter

[Atmos (Colin)]

A general rule of thumb is for a focal ratio of 5x pixel size and your setup there is right on that with 0.33”/pixel with a 5”.