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Synguider and ST80 aquiring stars question

LunarLight

By LunarLight
in Imaging - Discussion

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LunarLight

LunarLight

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Hey guys

Last night I thought I would test out my new auto guiding system but all did not go well.

I set up my NEQ6 got it aligned (its a heavy but awesome mount by the way) set up my scope then set up my guide scope: skywatcher ST80 and synguider but for the life of me I could not get the guider to detect any stars.

I even set the noise filter down to 3 and exposer length to maximum and nothing. I tried it with and without a diagonal. with and without a barlow (minus lens) as a extension but couldnt detect and stars at any focus setting.

I had a moment of success when I removed the 1.25" eyepiece attachment and just held the guider to the scope but that was it just a moment. I also tested it on my main scope and could find stars no problem.

I think its probably a focus issure, maybe I need to be closer in.

My question then is for those who own such a set up how doe you set your equipment up?

thanks

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AndyUK

AndyUK

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Hi there,

I think you may have a focus issue... Using a high mag star, I first get the imaging scope and guidescope in sync with each other (ie pointing at the same star) and then swap out the eyepiece (I use a 10mm) on the guidescope with the Synguider.

My process then is to set the noise to about 7. You should then see a "blob" on the Synguider screen (if the focus is WAY out, it may fill the screen, so you may need to pull it all the way in or out to see it as a "blob").

I then adjust the focus more carefully - As the "blob" gets smaller you'll notice the BRI value changing... You may need to adjust the exposure as you focus (with a high mag star, this can easily come down to 64ms or even 32ms)

I continue to adjust the focus until the "blob" looks to be about as small as I can get it, and then I use the zoom facility... and repeat again until at zoom level 4 and the "blob" is as small as I can get it (which at that zoom level is usually pretty big!)

That's when I know that it's focused as best as I can get it. You could then parfocalise an eyepiece so that you don't have to go through this again (my 10mm is kept specifically for the job - Just focus using the parfocalised eyepiece first and then replace it with the Synguider).

It's then a case of slewing to your imaging target, framing it and adjusting the position of your guidescope to pick up a suitable guide star on the screen. I personally usually use the auto select function and then lock a star (adjusting the noise level to increase / decrease the number of stars on screen).

I then adjust the exposure to get the BRI to around 15 or so. if it's too bright (or too faint) and the exposure is too low (or too high), I adjust the guidescope to find another guidestar and then relock it...

When the star is locked, the BRI is c. 15 and the exposure is not too high/too low, I select auto cal.... and after about a minute or it should be guiding.

Hope that helps...

Andy

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Photosbykev

Photosbykev

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to use a QHY5 ccd camera for guiding on my ST80 I ran out of focussing travel racking the camera outwards, this was without a diagonal fitted. I've fixed the problem by adding a normal x2 barlow nosepiece with the lens removed i.e it acts as a short extension piece maybe 15-20mm long.

Now I can focus precisely on stars with some adjustment on either side of the focus point.

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LunarLight

LunarLight

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Hey guys

Late reply as I have been insanely busy with university. The advice you guys cave is great! I will try one more time on the brightest star I can find at various different focuses then I will possibly have to consider an extention tube though I dont see why I should need one.

Since I uploaded this post there hasnt been a single clear sky! very annoying lol I will upload once I have a chance to test :)

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AndyUK

AndyUK

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I will possibly have to consider an extention tube though I dont see why I should need one.
As you'd normally use the ST80 for visual use with a diagonal, this effectively adds to the length of the light path. If you then remove it and attach the synguider direct to the ST80 (no diagonal), then the light path is effectively that much shorter, so you need an extension tube to bring it back out again... or, like me, you insert the Synguider nosepiece into the diagonal :(.

It's not the ideal way as there's apparently a higher risk of flexure, but it's worked for me to date...

(And yes, the weather has been totally cr*p for weeks!!! :))

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Psychobilly

Psychobilly

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An ST80 is on my shopping list ( as the OM wants his Equinoxe-66 back) and although using a diagonal is the last thing I would want to do with a guidecam at least it helps make the display readable...

I think I might tape the diagonal to make sure it cant rotate in the focuser

Billy...

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ollypenrice

ollypenrice

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I have just measured our ST80 guidescopes and the chip needs to be about 15cm from the back of the telescope, the black Hammerited casting from which the drawtube emerges. You can probably get this if you take the lens out of the Barlow with which mine came and use that an extension.

Flexure is not a problem if you make sure that black rear casting is tight (crosshead screws) and the drawtube lock screw is tight once focussed.

Peter, I too would have instinctively avoided a diagonal but now I'm not sure. If nice and tight it shortens the system and makes the screen visible as well. I had a guest using a diagonal successfully and he had a crisp litte setup that way.

Olly

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steppenwolf

steppenwolf

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Wherever possible, a diagonal should be avoided for flexure reasons but I'd make an exception for the SynGuider because of the position of the screen. Provided you tighten everything up before you start guiding AND ensure that you use a diagonal with TWO retaining thumbscrews it should work just fine.

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AndyUK

AndyUK

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Hopefully not hijacking the thread(?), but taking into account everything Billy, Olly and Steve have said, is there any view about whether the diagonal is 90 degree or 45 degree?

I can't think it would really make any difference, but I've tried using the 45 degree to date (on the basis that, for me, it makes it easier to see the screen).

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LunarLight

LunarLight

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Once again awesome advice, especially the 15cm distance required to focus the cam though I had no idea that the diagonal shortens this distance. Very useful information.

The sky is looking clear tonight so hopefully with the advice provided I might be able to produce my first guided image! :)

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Psychobilly

Psychobilly

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is there any view about whether the diagonal is 90 degree or 45 degree?

You will probably get a bit more light on to the chip with a buget 90 degree mirror compared to the budget 45 degree prism one ...

If the 45 degreee erect image prism type is working then stick with it...

At the end of the day its for a guidescoep and as long as you get usable guidestars then theres no need for anything too fancy as long as its all "tight"

Ordered my ST80 OTA today so will have it Monday... and Steve (FLO) says its the new "black" one - I knew there was a reason why I was hanging on before buying one :)

Billy...

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AndyUK

AndyUK

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Cheers Billy - It's worked to date, but if I get problems I'll know what to try.

Those black ST80's are VERY nice...! My ST102 is a black model too - I must admit I've often thought of seeing if I can trade it for an ST80 (to save me the 1kg extra weight), but as I'd really want another black one, I've not bothered!

The skies do appear uncommonly hopeful tonight, so I'm going to start setting up, but I do hope the skies are clear for you on Monday to try out your ST80!

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Psychobilly

Psychobilly

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Blue is so last Decade....

The 70-200 f4L USM is due on Monday to so foolishly I am passing on tonights clear skies as I still have to cable everything back up in the obs and rather do that in daylight...

Might pop out with a single cam on the EQ3-Pro later...

Or just shock horror do some "visual" with the 25x100's and try and find my way around the sky again.. its been way too long

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LunarLight

LunarLight

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woohoo I eventually got my guiding system working, I think the problem was that I wasnt getting the stars on the sensor correctly. Annoyingly as it took me a long time to get it figured out my DSLR battery was almost dead ha!

Here are a few comparison images, single frames and unedited. I am very much aware of coma being a big problem and im currently awaiting a adapter for a coma corrector I ordered.

this first one is without guiding, star trails and all: 5mins at io800

http://img841.imageshack.us/img841/5514/test059b.jpg

this second one is with guiding on, 5 mins at iso800. again no processing or anything. I think my set up wasnt great, maybe the focus is off slightly

http://img403.imageshack.us/img403/428/test058b.jpg

Thanks for all the advice guys I much appreciate it, now hopefully I can achieve a great image

Mark

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