Imaging woes

[Uranium235]

Hiya,

Just a quick question on imaging with a hyperion ep (17mm).

I gave it a go last week (on m42) but the results from my f5 newt were poor. Only 50% of the field was useable, anything outside that got ugly real fast (stars became streaks). Its a not tracking prob, otherwise all the stars would be streaks.

Would i get better results with an f5 if i removed the smythe part of the ep? Or should i just sack the idea of using a newt & buy an equinox APO?

The newt is fine @ prime focus, except there is no way i can use the 2" filter (or any other filter) without a lens or barlow.

Hmm i feel this is the start of an expensive and slippery slope! Lol...

[SteveP]

Uranium

It's a little difficult to diagnose your problem just from a description. It's usually best if you can post an image ...whatever it looks like.

However from your description, this sounds like a classical polar alignment problem where the region around the guidestar looks OK but stars away from the centre are exhibiting field rotation. It's a common problem based on the assumption that guiding is a universal panacea. IT ISN'T! You still need an accurate polar alignment to start with whether you're guiding or not

HTH

Steve

[Uranium235]

Here ya go.... the full horror

[Psychobilly]

Coma?

[Beyond_Vision]

yep coma

[Uranium235]

Hmmmm coma eh?

Will the MPCC fix this? And does it have a filter thread?

[brendant]

Stick to prime focus, trying to image anything other than the moon or planets with eyepiece projection will be very disappointing. Obtaining focus with most Newtonians and a DSLR's is very problematic as you have found out by not having enough "in" travel to achieve focus. Why not get a 2" nosepiece such as a MaxDSLR connector which has a 2" filter thread at the front for a light pollution filter, if you cannot achieve focus you need to either purchase a low profile focuser (expensive) or consider repositioning the mirror up the tube by 10-20mm. An MPCC will flatten the field of your Newt (not with an eyepiece in the imaging train though - at prime focus only) but you may still have the problem of not having enough "in" travel on the focuser

Brendan

[Uranium235]

At prime focus, im having no problem getting focus with the DSLR (a few mm to spare). Its just with the bits I have there is no option to insert a 2" filter between the secondary and the camera.

That MaxDSLR looks like the best bet to solve the filter issue, it looks to be more or less the same size the 2" T-adapter I use to do prime focus with at the moment (the one you get with the scope). Ordering it asap.

[SteveP]

Uranium

Every picture ....

That's not poor polar alignment. It's either a severe dose of coma like others have said or an equally bad dose of field curvature. I assume you can see how the star extensions appear to radiate from a central point.

Remind me again, why are you imaging through the Hyperion and not via prime focus? And why are you wanting to use a filter?

Steve

[Uranium235]

Im wanting to use the 2" Neodymium filter to help extend my exposure times in this light polluted area. I first used the ep to take moon shots (which actually turned out ok), and then tried my luck on m42 but i didnt expect that much coma. As was mentioned earlier, its probably better to save the ep method for planets.

Anyways, ive ordered the maxdslr adapter now, so next time its back to prime focus - hope it does the trick!

[ollypenrice]

I think it will...

Olly

[Uranium235]

Ya... just got the MaxDSLR, another thumbs up to FLO for speedy service.

And... its perfect! :eek: Its loads better than the one I was using as its even lower profile and it will let in a lot more light, which will reduce vignetting... chuffed to bits

M45 is going to get a right beating tomorrow nite

[brendant]

Good to hear it has worked out, the large bore through this adaptor means you have the least amount of vignetting possible on a DSLR chip. Have you managed to get a look at the stars to make sure you can achieve focus, if the answer is yes then a big thumbs up and look forward to some images.

Brendan