Jupiter - Still Struggling

[SnakeyJ]

I think you're spot on here Michael - to get the very best from our equipment and conditions, is going to demand some very close attention and careful tuning to reduce all the negatives that impact on our imaging.     I also am certainly in the more cavalier camp, doing a quick check with the long tube cheshire and laser before rolling the roof off the observatory.    Although I am using a cheap self centering adaptor and getting a good correlation between the laser and cheshire, there are many areas I am not covering.  Most notably:

a.   The ota is horizontal when I perform collimation, which is ignoring issues I almost certainly have with mirror flop on my stock synta mirror cell.

b.   This takes no account of the image train (filter wheel, barlow, extension tube and camera), which are highly likely to introduce orthogonality issues.

c.    I have a standard synta focuser with Lacerta 10:1 microfocuser and decent 2" compression adapter.   Though I have stripped and flattened the contact surface, there is undoubtedly a fair degree of slop, further compounding orthogonality issues.

d.   The image train may well be altered, depending on conditions and targets, by changing barlows and extension tubes.

There's undoubtedly a lot I can do here to improve the situation and this thread has really concentrated my thoughts on improving collimation and the image train to try and get the best out of what I've currently brought.     Sadly no money spare for the steeltrack or moonlight at the moment, as I've just spent my last pennies on a mirror recoat for another 8" newt (old Bresser Orion / Vixen R-200S)     It will be interesting to see how this performs with a 1/8 mirror, though allowing for the coatings to harden will put this back in late Jan/Feb, which will miss this opposition.

Neil - re your comments on the glow in the dark collimation cap, are you applying some glow in the dark paint or material to a standard collimation cap - or is this something your brought in the past.     I have a small lathe setup now, so will turn up and polish a nice mirrored collimation cap, that could be used with a clip light for indirect illumination.   But it would be simple to turn up another to glow in the dark if more useful outside in the dark.

[SnakeyJ]

Jake hope you don't mind my long winded takes on all this. I worry about going on so much, on others posts. Hope you find some good info in and around the discussions

Neil,

Absolutely not - it is a fascinating area, and I'm somewhat overwhelmed by the willingness and quality of advice that's offered.    I've been a member of many internet forums since the early days of usernet, mainly work related and SGL is truely an exceptional forum and community - a tribute to it's members and excellent moderation.   In many a thread like this would have descended in to a flame / personal war, and never developed to this extent.      As a real ale man, a pint of Abbots sounds excellent - though a wee drop of the good stuff is a rare treat and I have been a guest of the Bushmills Distillery on several occasions.

There has to be a balance between achieving the nirvana of optical perfection and in actually getting out and capturing some data!    I certainly need to raise my game and tune things to improve my chances, but a great deal to be said for a pragmatic approach to make the best of the limited favourable conditions/opportunities that arise.    

[cgarry]

Guys,

I like the longer discussions like these, I think they actually get everybody's point across better.  That is if the reader manages to wade all the way through the posts!

When I mentioned a star test I was not really talking about collimation, I have never owned a newt so would not presume to tell a newt owner how to collimate their scope.  What I was saying is that a star test is the simplest and fastest way to debug thermal problems with a scope, once these issues have been solved (fans, no dew heater, longer cool-down, insulating jacket, etc) there is probably no need to star test every time (though to be honest I do because it is so quick and easy to do and of course it is tied into SCT collimation).

I honestly don't believe that trying different fixes (turning off the dew heater for example) for a few nights and then seeing if the final images are consistently better is the way to go.  This approach may prove that one aspect of the thermal issues has been solved but there may be other problems remaining.  Just because the user saw an improvement in the final images over a few days does not mean that all the thermal issues have been solved and that seeing is now the limiting factor, there could easily be further thermal issues that need to be addressed to get their scope working at its full potential but these would be ignored.

When a star test only takes a minute and completely separates bad seeing from thermal problems it seems like a complete no-brainer to me and I can't understand the resistance to using them.  Though of course I fully accept that others have different methods that work for them.

I do agree that Neil and I are actually thinking along the same lines and are obviously trying to achieve the same thing.  However, whereas Neil is attempting to 'give a hungry man a fish' by telling him the probable causes of the issues I like to think that I am 'trying to teach the hungry man how to fish' by teaching him how to quickly identify and fix the thermal issues himself.

Cheers,

Chris

[neil phillips]

I think you're spot on here Michael - to get the very best from our equipment and conditions, is going to demand some very close attention and careful tuning to reduce all the negatives that impact on our imaging.     I also am certainly in the more cavalier camp, doing a quick check with the long tube cheshire and laser before rolling the roof off the observatory.    Although I am using a cheap self centering adaptor and getting a good correlation between the laser and cheshire, there are many areas I am not covering.  Most notably:

a.   The ota is horizontal when I perform collimation, which is ignoring issues I almost certainly have with mirror flop on my stock synta mirror cell.

b.   This takes no account of the image train (filter wheel, barlow, extension tube and camera), which are highly likely to introduce orthogonality issues.

c.    I have a standard synta focuser with Lacerta 10:1 microfocuser and decent 2" compression adapter.   Though I have stripped and flattened the contact surface, there is undoubtedly a fair degree of slop, further compounding orthogonality issues.

d.   The image train may well be altered, depending on conditions and targets, by changing barlows and extension tubes.

There's undoubtedly a lot I can do here to improve the situation and this thread has really concentrated my thoughts on improving collimation and the image train to try and get the best out of what I've currently brought.     Sadly no money spare for the steeltrack or moonlight at the moment, as I've just spent my last pennies on a mirror recoat for another 8" newt (old Bresser Orion / Vixen R-200S)     It will be interesting to see how this performs with a 1/8 mirror, though allowing for the coatings to harden will put this back in late Jan/Feb, which will miss this opposition.

Neil - re your comments on the glow in the dark collimation cap, are you applying some glow in the dark paint or material to a standard collimation cap - or is this something your brought in the past.     I have a small lathe setup now, so will turn up and polish a nice mirrored collimation cap, that could be used with a clip light for indirect illumination.   But it would be simple to turn up another to glow in the dark if more useful outside in the dark.

Hi  Jake yes its just purchased as is, with glow coatings already applied. try one, Made or otherwise, and see what you think. They are accurate and fast I find.

[neil phillips]

Guys,

I like the longer discussions like these, I think they actually get everybody's point across better.  That is if the reader manages to wade all the way through the posts!

When I mentioned a star test I was not really talking about collimation, I have never owned a newt so would not presume to tell a newt owner how to collimate their scope.  What I was saying is that a star test is the simplest and fastest way to debug thermal problems with a scope, once these issues have been solved (fans, no dew heater, longer cool-down, insulating jacket, etc) there is probably no need to star test every time (though to be honest I do because it is so quick and easy to do and of course it is tied into SCT collimation).

I honestly don't believe that trying different fixes (turning off the dew heater for example) for a few nights and then seeing if the final images are consistently better is the way to go.  This approach may prove that one aspect of the thermal issues has been solved but there may be other problems remaining.  Just because the user saw an improvement in the final images over a few days does not mean that all the thermal issues have been solved and that seeing is now the limiting factor, there could easily be further thermal issues that need to be addressed to get their scope working at its full potential but these would be ignored.

When a star test only takes a minute and completely separates bad seeing from thermal problems it seems like a complete no-brainer to me and I can't understand the resistance to using them.  Though of course I fully accept that others have different methods that work for them.

I do agree that Neil and I are actually thinking along the same lines and are obviously trying to achieve the same thing.  However, whereas Neil is attempting to 'give a hungry man a fish' by telling him the probable causes of the issues I like to think that I am 'trying to teach the hungry man how to fish' by teaching him how to quickly identify and fix the thermal issues himself.

Cheers,

Chris

Good analogy Chris. Though I do believe I might be trying to encourage a hungry man to better there fishing. But certainly with a eye on not bogging down the fisherman to the point where they can no longer be bothered to fish. Even talking about the basics we can certainly risk doing that. As is always hard to tell, with quick discussions on a astronomy forum. As time has gone on. I  would not put Jake in that camp. So perhaps a certain amount of fishing tuition is helpful

You know Chris I spent many years staring at stars with my 245 mm Orion. Mainly to determine cooldown. So I fully agree it is indeed a powerful tool we can use. However after fitting fans ( I now use two ) and such said star tests show using both fans, the optics are free of plumes and such, in quite a quick period of time. its variable. But a hour will usually suffice.

I am now to a point that with the Orion I no longer need to star test for thermals. As I run the fans ( I switch to the back fan ) in periods all night.

Mainly to keep track with falling temps. Star testing for thermals is no longer needed. And even if the scope optics were not cooling for some odd reason ( I haven't seen this ) there is little I could do that I am not already doing. Other than peltier coolers. Which is probably overkill for 245 mm optics. Especially as I am aggressive using two fans already.

So its just not needed anymore with such aggressive cooling. There are not many more things for the Orion that I would need to star test for. I make sure my barlow and filters have time to cool. Something a lot of people may overlook.

The 12" may be a different matter if I wanted to be very thorough. I could be testing different strengths of fan that I am using agreed. But its small seems to be doing a good job. Larger fans do run the risk of more vibration. Even though I am using a baffle de coupled from the scope using rubber bands

I am about to try camping mats as dew shields, very cheap. And extremely light. So after cooling I may well test on a star to see if the material is just bad news or not. I hope its ok to use, as I cant believe how light this is. Much lighter than commercial shields one can buy. It seems to me, to be a bad material thermally to be using. But I will see how it fairs once its been in the freezer. And left to rise to ambient again.

There really is a limited amount of things that need checking for thermals Chris ?  Optics cool down.I have that covered, dew shields covered. Camera filters and lenses covered.

Other than re designing a telescope. Lets say with different tubes or cells. There is really very little that needs continual star testing for in my opinion. Am I missing something here ? As I believe  if its needed I tend to try it. As mentioned I did for years.  But there hasn't really been a reason of late to do so ?

Seeing that my 12" primary needed active cooling was obvious from the images live on screen, As I could easily tell it was struggling to keep up with falling temperatures. It would start out in focus, by the time I got to the blue it was completely out. This was just as informative as star testing ? Though the only thing I may be overlooking is the strength of the fan. Agree with that Chris. Something I might look into, but its not easy. as I only have one baffle. And would need a larger fan to test.

 There is no other thermal issue I could do much about that wouldn't require a telescope re design. Something I do not really have the budget for ?

So to clarify. Once the collimation question is covered. And we have covered that. I do believe I agree star testing can be useful. Just not always needed. And sometimes its almost certainly moot. Depending on the situation

[neil phillips]

I think you're spot on here Michael - to get the very best from our equipment and conditions, is going to demand some very close attention and careful tuning to reduce all the negatives that impact on our imaging.     I also am certainly in the more cavalier camp, doing a quick check with the long tube cheshire and laser before rolling the roof off the observatory.    Although I am using a cheap self centering adaptor and getting a good correlation between the laser and cheshire, there are many areas I am not covering.  Most notably:

a.   The ota is horizontal when I perform collimation, which is ignoring issues I almost certainly have with mirror flop on my stock synta mirror cell.

b.   This takes no account of the image train (filter wheel, barlow, extension tube and camera), which are highly likely to introduce orthogonality issues.

c.    I have a standard synta focuser with Lacerta 10:1 microfocuser and decent 2" compression adapter.   Though I have stripped and flattened the contact surface, there is undoubtedly a fair degree of slop, further compounding orthogonality issues.

d.   The image train may well be altered, depending on conditions and targets, by changing barlows and extension tubes.

There's undoubtedly a lot I can do here to improve the situation and this thread has really concentrated my thoughts on improving collimation and the image train to try and get the best out of what I've currently brought.     Sadly no money spare for the steeltrack or moonlight at the moment, as I've just spent my last pennies on a mirror recoat for another 8" newt (old Bresser Orion / Vixen R-200S)     It will be interesting to see how this performs with a 1/8 mirror, though allowing for the coatings to harden will put this back in late Jan/Feb, which will miss this opposition.

Neil - re your comments on the glow in the dark collimation cap, are you applying some glow in the dark paint or material to a standard collimation cap - or is this something your brought in the past.     I have a small lathe setup now, so will turn up and polish a nice mirrored collimation cap, that could be used with a clip light for indirect illumination.   But it would be simple to turn up another to glow in the dark if more useful outside in the dark.

Its certainly worth raising the scope elevation Jake when collimating the primary, as it may well move. I just raise it to the elevation and middle angle of the part of the sky I will be imaging in.  and adjust the primary. Its actually quite easy with a laser to see when its collimated at high elevation. Only takes a few secs to raise the scope up. Worth doing for sure. Ive wondered about self centring caps to reduce focusser slop. Not sure if they work or are variable or what. There is reasons for me that doing star collimation using software and using my imaging train. May not be as precise as I would like. Due to mirror flop. Focuser flop plays its part too. And even if a star was very close to Jupiter to minimize primary flop. By the time I took the camera out put a eyepiece in centred Jupiter. Put the camera back in. I run the risk of the focuser angle ( slop ) ruining the collimation Star collimation had just achieved. But agreed I should get a new cell. But without a new tube I cant do it. Its often damage control for me. Even though I would like the perfect setup.

[Freddie]

This has been a very interesting read. Nobody can doubt the excellent results you lot are getting, so evidently, there is no single "right" way of doing it. I must say I am generally fairly cavalier in my attitude to collimation, as my C8 seems to hold it very well indeed. On the other hand, my results to date aren't anywhere near as good as yours, so I might well pay more attention (once the clouds have buzzed off (some time after the next 14 days according to the current forecast).

MetaGuide (free download) is well worth a look as it is very good for checking and fine tuning the collimation on SCTs

[michael.h.f.wilkinson]

MetaGuide (free download) is well worth a look as it is very good for checking and fine tuning the collimation on SCTs

Cheers, Freddie, I may well try that once the clouds have gone

[Kokatha man]

Quote <"So to clarify. Once the collimation question is covered. And we have covered that. I do believe I agree star testing can be useful. Just not always needed. And sometimes its almost certainly moot. Depending on the situation>"

The preceding are Neil's words but I'm really not interested in whose they might be for the purpose of this topic - but let me clarify what seems to be encapsulated in these comments - and it really is of no consequence whether you use a Newt, SCT or any other scope (naturally with a refractor this is unlikely to be an issue, and if able to be collimated could be an onerous task: Maks I have nfi about but believe they hold collimation well as do some other types of optics...but the issue is the same with all scopes ultimately.)

"Star-testing" as I have used the term is an aspect of collimation...or in my usage actually refers to collimating, so it is neither "moot" nor unnecessary!!!!

It is, when taken to the degree of Airy Disk refinement THE most accurate method of collimating.....and whether you simply do this onscreen manually or use software like Metaguide as Freddie has suggested is entirely an individual's choice.

Also, whether you wish to do this each & every time you image is your own decision...but I'd suggest that anyone who wishes to optimise their imaging outcomes each & every time should do so....!

Naturally the sky conditions might make folks want to rush these preliminaries but I have already articulated our own experiences when we break what we consider a "Golden Rule" for us - but then again I accept that plenty of other folk don't have my obsessive desire to extract the maximum out of every imaging possibilities - and that's also highly understandable!  

In fact I don't use the Airy Disk myself for reasons that I articulated elsewhere not that long ago but in saying that I do so because I have learnt to interpret the Diffraction Ring patterns to the degree that I believe is commensurate with fine AD adjustment and saves time for me by doing so...just as I no longer do quick "on the fly" captures & processing to elicit the state of collimation (although this is a very good suggestion for those who are learning the ropes with this and don't use Metaguide etc.)

But whatever you do or don't do there is no substitute for "in camera" collimation which must employ the term that has been bandied around somewhat loosely at times in this thread - ie, "star-testing."

Whether an individual does this or not is their own choice but I'd recommend anyone doing so themselves for a few nights (to give themselves the chance to strike some decent seeing for starters!!!  ) and this way you'll be confident of what you're doing and absolutely ensure you'll get the best possible imaging outcomes once you understand what you're doing!

That's really it for me - over & out!      

[neil phillips]

Well those comments were really for Chris Darryl. I did Not turn the conversation into just in camera collimation, but it is fast turning into that. The comments I made that you quoted actually refer to when Chris said this

When I mentioned a star test I was not really talking about collimation, I have never owned a newt so would not presume to tell a newt owner how to collimate their scope.  What I was saying is that a star test is the simplest and fastest way to debug thermal problems with a scope, once these issues have been solved (fans, no dew heater, longer cool-down, insulating jacket, etc) there is probably no need to star test every time (though to be honest I do because it is so quick and easy to do and of course it is tied into SCT collimation).

So when I said

Once the collimation question is covered. And we have covered that

I meant everything to do with the collimation. Both telescope and in camera. As we have been discussing that.

When I said

 I agree star testing can be useful. Just not always needed. And sometimes its almost certainly moot. Depending on the situation

I meant Star testing in terms of checking for thermal problems. That's all, no Negative comment directed at in camera collimation in the slightest.

Now I highlighted your bolds. SGL has made me bold too  

[Kokatha man]

.....my comments are for anyone reading this thread Neil  and how they might interpret anyone's comments: I think my last post fully-articulates my own views!

[neil phillips]

.....my comments are for anyone reading this thread Neil  and how they might interpret anyone's comments: I think my last post fully-articulates my own views!

Yes I was just confused why you highlighted the moot or unnecessary statement by me, to mean. your usage referring to collimating as being moot or unnecessary ?

Star-testing" as I have used the term is an aspect of collimation...or in my usage actually refers to collimating, so it is neither "moot" nor unnecessary!!!!

As I wasn't referring about collimation just seemed confusing to highlight it in such a way as it kind of looked like I did mean that ?  

As I wasn't talking about your term. That seems quite confusing too. For anyone reading this I was referring to thermal issues not collimation when I said this.  

I am pretty sure you can see how that might look like I was suggesting star testing for collimation purposes was both moot and unnecessary. I certainly was not.

Hope that's cleared up.

[Kokatha man]

.....well, I've gotta admit that your comments were confusing to me Neil, so it's good that you've clarified them!

Also, that last longish post by me allows me to be quite specific about my own views etc.....and just to re-emphasize them I conflate "star-testing" to mean both collimating & seeing appraisal, as well as what's happening in the OTA as far as heat is concerned - so it really is not only the best/most accurate method of tuning a scope imho, but has these bonuses as well!!!

Folks might well have reasons for not doing it this way, but that is an individual's choice and at best does little or even no harm...but at anything less than that possibility can only be to the detriment of the imaging outcomes!