Focussing between filters on planetary imaging

[aqualand]

just wondering what people do for focussing different filters with a mono planetary camera?

Im assuming there aren't likely to be any stars in the field of view so you'd have to slew to a star refocus and slew back to the planet.

Does that cause problems if you're not spot on when you slew back, or does it not really matter given your taking a video for each filter that then gets combined in post processing?

Any advice or issues people have come across very welcome.

For info i'm thinking of using the mono version of the qhy5-ii as this will be a guidecam as well.

Thanks

Garry

[lensman57]

just wondering what people do for focussing different filters with a mono planetary camera? Im assuming there aren't likely to be any stars in the field of view so you'd have to slew to a star refocus and slew back to the planet. Does that cause problems if you're not spot on when you slew back, or does it not really matter given your taking a video for each filter that then gets combined in post processing? Any advice or issues people have come across very welcome. For info i'm thinking of using the mono version of the qhy5-ii as this will be a guidecam as well. Thanks Garry

There are a few issues you need to consider.

1- Are your filters parfocal to each other?

2- is your telescope well corrected for all wavelengths? APOs, MAKs, SCTs and Newts will be fine, Achros and EDs will not

3- Is there a bright Star near the target?

You focus on a bright star near target  and if conditions 1 and 2 are met just rotate the FW and carry on.

Hope this helps a bit.

A.G

[aqualand]

Thanks Lensman,

I'm using a newt but may consider purchasing a MAK/SCT in the future so condition 2 should be fine.

With regard to parfocal filters, I take it not all filters are the same so does that mean buying all from a particular set?  Looking at the likes of First Light optics only one set on there specifically says they are 'very nearly parfocal'.

Thanks

[glowingturnip]

fwiw my colour qhy5lii works fine as a guide cam

[aqualand]

Thanks Stuart,

I was toying with the colour but though this would be a 'cheaper' step up to mono and give me some practise in that side of things as well.

Happy to be shot down in flames from some of the more experienced imagers on here

Cheers

[glowingturnip]

oh no no no, I was wondering which to get when i got mine, but plumped for the colour.  Didn't fancy the faff of filters for planetary

[aqualand]

Stuart,

Just had a look at your flickr picteures and there are some good images on there.  I take it the 'kit' photo is taken at your dark site in Spain, not sure i'd be happy with my kit setup so close to the pool

[glowingturnip]

haha cheers mate ! 

Yes, So far have only managed to drop a couple of lens caps in it, and haven't yet fallen in myself wandering around in the dark, though I'm sure it'll happen.   Apart from the pesky pool though, it's the perfect spot for it

[lensman57]

Thanks Lensman,

I'm using a newt but may consider purchasing a MAK/SCT in the future so condition 2 should be fine.

With regard to parfocal filters, I take it not all filters are the same so does that mean buying all from a particular set?  Looking at the likes of First Light optics only one set on there specifically says they are 'very nearly parfocal'.

Thanks

Newtonian is fine as the mirror does not refract the rays so there is no issue with fringing . Yes you  do need to get them as a set but these parfocal ones are not cheap. The names to go for are the Baader LRGB set, the more expensive set not the cheap one, Astronomik LRGB Type iic, these are expensive any way but they are optimised for 1:1:1 weighing and if you have deep pockets you may consider Astrodon filters. 1.25" versions are more than adequate for webcam imaging but if you think that in the future you'd be doing DSO imaging with a large Mono CCD then give consideration to the 2" versions, these are quite pricy though.

Regards,

A.G

[aqualand]

Thanks again Lensman, lots to think about, and money to save.