Bahtinov Mask advice

[Dielectric]

Does a Bahtinov mask help in achieving good focus for planetary CCD imaging? Are they any good?

Sorry if this has been answered elsewhere.

Cheers

Arif

[Tantalus]

When it comes to focus masks, Bahtinovs are probably regarded as the best thing since sliced bread! Have a look at this thread:- http://stargazerslounge.com/equipment-discussion/95787-bahtinov-style-focus-masks.html Coincidentally, I was making one earlier this evening.

[Dielectric]

Thanks for this- I just had a read and they certainly sound almost like an essential for imaging. The one point (there's always one- sorry!) I remain unclear on is whether they will help achieve good focus on planetary imaging through a CCD looking on a computer screen?

I use a DMK21 CCD through an f10 SCT for capturing planets. To get good focus would I need to focus on a star point first the use this as prime focus for the planet- is this a viable method?

Many thanks

Arif

[Psychobilly]

Yes they work.. but its better to focus up on a nearby bright star and then slew back...

On an extended object you get diffraction "bars" rather than spikes these still move back and fore across the 'X' but its harder to determine the exact position...

If the planets is showing phase you actually get lines of the "phase" looks cool ....

Peter...

[Dielectric]

Great- Thanks for the advice-really helps. I will probably order one rather than make one. There is a retailer called Stay Focused which sells them.

Cheers

Arif

[steppenwolf]

I agree with Peter (and trust me, he knows!) - use a bright star and then return to your planet. What I normally do is make this part of my alignment process - once I have slewed to my first alignment star, I use this to focus on using the Bahtinov Mask as this negates any image shift problems due to focus tube slop later on in the session.

[Demonperformer]

I will probably order one rather than make one.

Before purchasing, you may wish to check out the easier-to-make alternatives offered in this thread: http://stargazerslounge.com/beginners-help-advice/100737-focussing-through-dslr.html

[Dielectric]

Dear All

Hey thanks for this- Must admit I am accident prone with sharp objects. The thread on focussing on a DSLR is fascinating. Had no idea there were so many methods of achieving focus.

Well I am truly grateful for all the intuitive responses- now where's that Stanley knife....

Cheers

Arif