Trouble collimating a Helios Apollo 150 Newtonian (f/6.67)

[iam4208]

I've been trying to collimate this 6" scope since I started to notice difficulties in focussing with a 10mm Plossl (100x magnification).

Only the moon looks reasonably in focus with the 20mm Plossl (50x magnification).  Everything else looks off.  Stars have severe flaring and Jupiter is a blurry blob with hardly any detail, when I used to be able to see a nice bright disk with two dark bands across it.

To cap it all the flaring on stars changes direction depending on which way you defocus, making star collimation very difficult (adjust so that star moves in the direction of the flaring).

This has stumped several experienced observers who have all had a go at improving things and I'm beginning to think there is another problem with the scope.

To make things really awkward, this scope has a corrector lens in front of the secondary mirror and the secondary mirror position is not user adjustable, according to someone who had the same model.  This rules out the use of laser collimators and I can't see an easy way to remove the corrector lens temporarily, as suggested on a very old post (I know some scopes have the corrector lens in the focusser and it can be removed).

However, when checking the secondary alignment, I cannot see the primary mirror clips, as advised by just about every collimation guide on the planet.

Celestron produced a similar scope called the C150-HD, so I'm hoping someone out there has or had one of these or the Helios and can provide some explanation as to why this thing does not focus at higher magnifications or can advise on how to check and adjust the collimation with confidence.

Maybe the corrector lens has somehow moved!

[Langy]

Have you thought about contact a couple of Astronomy shops?

I think that http://www.scopesnskies.com/ are a reasonable size retailer, might be worth giving them or someone similar a call.

[iam4208]

No, I didn't think they would be interested, since the scope is so old.  I'll try one and see what happens, but I honestly think this problem is beyond most people!

[Langy]

Worth a phone call, a lot of places are often keen to give advice and help.

A long shot but Alan from Scopes And Skies may also be a name, but he is as far as I know web based mainly through eBay, he gave plenty of advice to me even though I was making a purchase but he wasn't to know.

[iam4208]

Okay, I've got time off on Friday to give them a call.  Someone had a go at collimating it last night and it has improved slightly to the point it's usable at 100x magnification or lower.  However, even they admitted that it wasn't quite right and that they would consider examining/tinkering with the secondary if I could get some information on it's assembly.

[iam4208]

Okay, a fellow observer has made some progress with this scope, by doing some collimation/alignment of the secondary. Unfortunately, the poor weather in Scotland has scuppered all opportunities to conduct a star test. The saga continues..

[TrickySpot]

I've been trying to collimate this 6" scope since I started to notice difficulties in focussing with a 10mm Plossl (100x magnification).

Only the moon looks reasonably in focus with the 20mm Plossl (50x magnification).  Everything else looks off.  Stars have severe flaring and Jupiter is a blurry blob with hardly any detail, when I used to be able to see a nice bright disk with two dark bands across it.

To cap it all the flaring on stars changes direction depending on which way you defocus, making star collimation very difficult (adjust so that star moves in the direction of the flaring).

This has stumped several experienced observers who have all had a go at improving things and I'm beginning to think there is another problem with the scope.

To make things really awkward, this scope has a corrector lens in front of the secondary mirror and the secondary mirror position is not user adjustable, according to someone who had the same model.  This rules out the use of laser collimators and I can't see an easy way to remove the corrector lens temporarily, as suggested on a very old post (I know some scopes have the corrector lens in the focusser and it can be removed).

However, when checking the secondary alignment, I cannot see the primary mirror clips, as advised by just about every collimation guide on the planet.

Celestron produced a similar scope called the C150-HD, so I'm hoping someone out there has or had one of these or the Helios and can provide some explanation as to why this thing does not focus at higher magnifications or can advise on how to check and adjust the collimation with confidence.

Maybe the corrector lens has somehow moved!

I'm not sure how you'd start a thorough collimation without being able to adjust the secondary, its step 1 in most collimation guides. Perhaps with some help of a pro, the secondary 'module' can be disassembled and checked. Also, the mirror clips have never ever been visible in my MN190, so don't take that as a definite for your model unless other owners confirm they can be visible!

Hope you come right!

[iam4208]

Can't do much until the weather improves.

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