collimation for astrophotography

[Gerhard]

Hi all,

yesterday had the first session in the AP seminar I'll befollowing this november.

I asked some advice about my first scope to buy (obviously) having AP in mind, and they were quite adamant that it would not be a good idea to buy a Newton for that, as you would have to collimate almost every time you go out shooting, and that laser collimation wasn't enough, but one should collimate pointing at the stars as well (don't know if that makes sense, it was the first time I heard one could do this... I didn't insist on having this explained to me...)

So ,they were very much like "buy the ED80, not the 130PDS....", also for fogging reasons...

Opinions on this? is collimation really THAT important and precise with AP?? NB: for good shooting I will probably always have to go out in the car, so not leaving the scope in its place...

thanks as always!! :-)

Gerhard.

[Gerhard]

I should specify: it's not the collimation that perplexes me. As many have written, after a few times you do this, it gets routine, and you do it in 1 minute, so even if one has to do this every time out, that's ok. But the "star collimation" aspect had me worried a little....

I had my mind set on the 130 or 150 PDS...

[rowan46]

yes collimation does need to be precise else focus will not be great and the stars will be fuzzy as all the colours wont come to a point  which is why the ed80 is the preferred starter scope for imaging. Having said that there are some pretty decent images taken with the 130pds and new they are a whole lot cheaper. They certainly appear to work very well if you can get them well collimated

[Gerhard]

do you know anything about the "star collimation" thing? it's supposed to be ultra precise collimation, and essential for quality images...

[laser_jock99]

Gerhard,

I don't know who these people were - but they obviously no experience with modern collimation techniques! For critical AP the collimation needs checking before each session- but this should only take a minute or so (assuming it's still close from last use). I only use a 2"  quality laser collimator there are some cheap ones around which should be avoided.

[Gerhard]

So that talk about collimation using the stars?

The person talking is the one presenting the AP seminar, so he obviously has been around the block a few times....

That said, I was also surprised he said there is more to collimation than "just" a laser collimator.....

[tingting44]

the 130-pds is a great scope, here is SGL's 130 imager's

http://stargazerslounge.com/topic/210593-imaging-with-the-130pds/

and yes a star test for collimation is like fine tuning after using the chesire to get it close...

http://www.willbell.com/TM/tm5.htm

[Gerhard]

I'll need to buy that too, besides Making Every Photon Count... :-)

[tingting44]

I'll need to buy that too, besides Making Every Photon Count... :-)

you wont go wrong spending your money on a chesire and "THE" book

[Gerhard]

The Cheshire will have to wait until I know what scope I'll be buying and so if it needs to be a 2 or 1,25" tube...

[Gerhard]

The Cheshire will have to wait until I know what scope I'll be buying and so if it needs to be a 2 or 1,25" tube...

[tingting44]

i use this 1.25" chesire

http://www.firstlightoptics.com/other-collimation-tools/premium-cheshire-collimating-eyepiece.html

with my 2" self centering adapter, win, win

http://astronomia.co.uk/index.php/accessories/adaptors/alt-aa-sca-2-125.html

but yes you wont need the above if you get a frac

[laser_jock99]

i use this 1.25" chesire

http://www.firstlightoptics.com/other-collimation-tools/premium-cheshire-collimating-eyepiece.html

 

with my 2" self centering adapter, win, win

http://astronomia.co.uk/index.php/accessories/adaptors/alt-aa-sca-2-125.html

 

but yes you wont need the above if you get a frac

Yes - it's important to consider the extras when deciding which scope to buy. For a refractor you'll probably need a field flattener/corrector matched to the scope. Possibly a dew heater as well.

For a reflector you'll need the collimation tools and a coma corrector. It may be a bigger scope (for the same price) so might need a correspondingly larger mount.

[Gerhard]

@laser_jock: just out of curiosity, as I was reading your signature: you seem to have like 8 different scopes!! where do you store all those?? do you live in a farm? :-)

and in how many years have you bought all those?? do all you guys take out a mortgage for the astronomy stuff??? :-DD

[laser_jock99]

@laser_jock: just out of curiosity, as I was reading your signature: you seem to have like 8 different scopes!! where do you store all those?? do you live in a farm? :-)

and in how many years have you bought all those?? do all you guys take out a mortgage for the astronomy stuff??? :-DD

Gerhard- the scopes have taken me 6 years to collect- but I think I have stopped buying for now.....

I'm lucky to have a large observatory so storage is not a problem.

[dph1nm]

Opinions on this? is collimation really THAT important and precise with AP??

It might be if you have sub-arcsecond seeing where you live, or an F2 astrograph,  but otherwise I don't see why it has to be any better than for visual use.

NigelM

[Gerhard]

@Nigel: no, and no.

so... :-) star testing will be a sidekick hobby... :-) Maybe to try once in a while to see if my collimation was spot on... :-)