Things not to under estimate in imaging

[swag72]

Here's another I discovered last night after Maxim failing to sort out the guiding.

- Never under estimate the power and mending abilities of disconnecting everything and switching the computer off and on again. How it does it, I'll never know. But I should know by now that it is something worth exploring earlier rather than later in the evening as I wasted almost 2 hours with the guiding. Had I tried this miracle cure earlier I may have got my 5 hours worth of subs!!

[squeaky]

There's a maxim that many of us hairy old engineers work by...

90% of all problems can be solved by one of the three SIMPLEST answers you can think of.

[JamesF]

There's a maxim that many of us hairy old engineers work by...

90% of all problems can be solved by one of the three SIMPLEST answers you can think of.

I think that's the engineer's version of Occam's Razor

James

[Dave Smith]

Hi Sara, that is a wonderful collection of points. If you don't mind I will use this in a talk on imaging to my club soon. The one I am having difficulty in persuading people about is no 3 (Exposure time in hours). People seem so happy to have taken something like 8 x 2minute subs and wonder why their image is not so good. The next one is no 8 (Focusing) - "well it's almost in focus"

Thank you for this post - most interesting.

Dave

[swag72]

Glad it's been useful to you Dave - Regarding imaging in hours as opposed to minutes, can you not come up with some real live examples - Should be fairly easy to do a comparison between the two and show the difference nicely.

[Dave Smith]

Glad it's been useful to you Dave - Regarding imaging in hours as opposed to minutes, can you not come up with some real live examples - Should be fairly easy to do a comparison between the two and show the difference nicely.

Good idea

Dave

[Martin-Devon]

Thanks for the great post Sara - the points you make & the additions by others makes for excellent reading whether you are a beginner or relatively experienced. I'm still struggling to some extent to get spot-on PA, many times I've read that the guiderscope/PHD will take care of this, but I'm not convinced. Also what you say about rebooting the PC is something I've needed to do several times - also for unknown reasons the exact order I connect the power supplies & USB cables into the powered hub seems to be very important otherwise all I keep getting is "failed to recognize the CCD" etc, and when that fails (and it does) I resort to a reboot - one way or the other everything finally connects but sometimes it's really finger-crossing time and very frustrating.

I would welcome more posts like this though, well done for sharing your experiences in imaging

[squeaky]

Camera counterweights on an Auto/Goto Dobsonian.

My DSLR camera plus adaptor weigh 663 grams - and they are twice as far from the pivot point as the mirror is.

I checked this because the other night with an alignment star in the centre of my view I very carefully sat my Bahtinov mask in place, only to find that the star had moved to the very edge of the field of view. If that's what a lightweight sheet of fibre stuff can do to my 12" dob there's no wonder I've been having problems guiding and tracking. Sheesh!

So I need 1220 grams of weight at the bottom end of my OTA.

That works out ( for proof of concept purposes) at...

1 tin baked beans

1 tin peas

1 tin Spam

Who knew?

Richard, wondering where the parcel tape is....

[MikeWilson]

Very good list and followup

I'd also add this: shorter focal lengths and lighter equipment is more forgiving on the back and the tolerances of the setup but not on the bank balance.

Getting bang on polar alignment isn't such a big deal if you have your guiding well configured. Clearly an advantage to a pier-based-setup is to get everything spot on but for mobile folks I'd say spend more of your time on balance and focusing and not worry about the PA too much as long as Polaris is approximately correctly placed.

[nmoushon]

Getting bang on polar alignment isn't such a big deal if you have your guiding well configured. Clearly an advantage to a pier-based-setup is to get everything spot on but for mobile folks I'd say spend more of your time on balance and focusing and not worry about the PA too much as long as Polaris is approximately correctly placed.

This is first I've seen it said on this thread but can't agree more with balance. In regards to how the telescope is balanced with the appropriate weights as well as making sure the tripod is balanced as well. Don't know how many times I've over looked balancing the tripod and the wondered how come I'm getting star trails after 60sec where they normally dont show till around 90sec. And of course don't realize what the problem was until half my night is gone.

[icrusoe]

Very good points! And an awesome gallery to back them up!

[Chris]

read it, nodded, smiled:)

[springbok]

Thanks Sara, all very good points for a starter in imaging like myself.

[OzDave]

This is first I've seen it said on this thread but can't agree more with balance. In regards to how the telescope is balanced with the appropriate weights as well as making sure the tripod is balanced as well. Don't know how many times I've over looked balancing the tripod and the wondered how come I'm getting star trails after 60sec where they normally dont show till around 90sec. And of course don't realize what the problem was until half my night is gone.

How do you balance a tripod? Do you mean levelling?

David

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[swag72]

You can't balance a tripod. In this case, the poster is referring to balancing a mount with the counterweights I would assume.

[OzDave]

You can't balance a tripod. In this case, the poster is referring to balancing a mount with the counterweights I would assume.

Well, no, the poster refers to balancing with counterweights as a separate point and explicitly refers to balancing the mount. I'm wondering if the poster meant levelling the mount because levelling an EQ mount isnt necessary so long as you are polar aligned.

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[DazC]

Great thread, some very usefull points for a beginner in ap like me.

Thanks to everyone.

D.C

[nmoushon]

How do you balance a tripod? Do you mean levelling?

David

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Sorry for the mix up. I did not mean balancing the tripod. I ment making sure it was level. Thanks for the catch.

And leveling does affect polar alignment. Though small that it might be it does effect it. If the mount is not close to level you will never be able to get very good alignment. It doesn't have to be spot on. If you use guiding then its less of an issue. But for those of us, like mtself, that don't use guiding leveling can mean the difference between getting only 90sec subs instead of 110-120sec subs. When subs are that short to begin with every sec really adds a lot to the final image.

[OzDave]

Sorry for the mix up. I did not mean balancing the tripod. I ment making sure it was level. Thanks for the catch.

And leveling does affect polar alignment. Though small that it might be it does effect it. If the mount is not close to level you will never be able to get very good alignment. It doesn't have to be spot on. If you use guiding then its less of an issue. But for those of us, like mtself, that don't use guiding leveling can mean the difference between getting only 90sec subs instead of 110-120sec subs. When subs are that short to begin with every sec really adds a lot to the final image.

Agreed, levelling does make polar alignment easier. This is because levelling makes the alt/az adjustment bolts operate in alignment with the actual altitude and azimuth axes. Thus making an adjustment to one does not affect the other axis. However, if the mount is not level, adjustments in one axis cause a displacement in the other axis, which may have been ok.

That being the case, it is still possible to have your mount not level, even very not level. You could have it mounted on the wall of your house if you like. So long as you can get the alt/az bolts to point the polar axis correctly you will be ok. Of course, this is likely to be relatively difficult for the reasons outlined above.

David

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[Quatermass]

Great thread have to agree on so many points. For me three things really stick out getting your focus dead right, good dark skys with lots of subs and learning the art of processing. Add to that a well balanced setup charged batterys and practise practise practise plus all the great encouragement you get on sgl

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[Austin]

That is all sound advice Sara!

I am on the cusp of venturing from the world of visual observing to that of AP, and I will be taking all of the points on this thred very seriousely!! soooo many choices ahead!!

Clear and dark