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ARP 285

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#1 Mike7Mak

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Posted 05 January 2013 - 05:28 AM

Well can't blame the Moon for this one but conditions continue to be a challenge. Seeing is still ragged and I've seen more stars under the full Moon.

I have to say though I'm pretty impressed with the OAG given the radical difference between the PHD graph at 1800mm and 700mm. The graph excursions 'look' so much worse I can't believe the stars I'm getting. Even though they are bloated from the seeing they're still relatively round.

This pair is ARP 285. Minimal processing, just some sharpening of the galaxies, 70% bin, and no star tweaking what-so-ever.

27 x 3 minutes

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#2 Mike7Mak

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Posted 05 January 2013 - 05:51 AM

Here's a couple crummy shots of the OAG...

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#3 Mike7Mak

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Posted 05 January 2013 - 05:52 AM

And...

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#4 Mike7Mak

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Posted 06 January 2013 - 12:52 AM

I managed to grab a couple hours right after sunset before the clouds rolled in tonight. Conditions seem to be improving. Tightest guiding so far with the OAG.

This is ARP 74.
Posted Image

Here's a couple more I collected over the last few days. Kinda marginal but thanks to StarTools I was able to make them somewhat 'presentable'.

ARP 243
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ARP 270
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#5 Peter in Reno

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Posted 06 January 2013 - 01:11 AM

It's perfectly normal for PHD graph to look worse at longer focal length. It's because the unit is in pixels instead of arcsecs. PHD has no idea what's the image scale of your camera/scope setup.

I am willing to bet that if it was converted to arcsecs based on the image scale of the guide camera/scope, the graph would look better at longer focal length using OAG as opposed to shorter focal length guide scope.

Excellent images and guiding!!! OAG is the best way to get round stars.

Peter

#6 Mike7Mak

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Posted 06 January 2013 - 02:52 AM

Hi Peter thanks.

Yes I understand why, but I have to admit I haven't done more than a ballpark estimation with CCDcalc. The DSIpro2 on the 70mm piggyback refractor runs about 2.5 arc/sec pix and through the Mak 7" w/OAG at 1800mm it's around 1 arc/sec pix.

Sooo let's see, with the refractor I average .20 to .35 RMS in PHD pixels. Tonight through the OAG I was running around .65 to .85 RMS. That seems reasonable although I'm not up for quantifying the actual improvement, or lack thereof. :)

#7 rigel123

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Posted 06 January 2013 - 09:14 AM

Looks like a nice, neat setup Mike! The images are very encouraging given the skies you have been imaging under. I really need to get off the beaten path a bit and try some objects like these!

#8 dickbill

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Posted 06 January 2013 - 10:21 AM

Good job.
Mine oag is the orion, i don't use it much because it's so hard to find a guide star. I wish the'd put some sort of bigger mirror to increase the field of view. To me, a flip mirror with a central hole big enough to illuminate a 1 cm X 1 cm (~1/2 inch) chip would be ideal.

#9 CounterWeight

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Posted 06 January 2013 - 12:41 PM

Mike - very cool, love these images you are putting up, you are the groups Arpster' !

#10 Mike7Mak

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Posted 06 January 2013 - 03:28 PM

Good job.
Mine oag is the orion, i don't use it much because it's so hard to find a guide star. I wish the'd put some sort of bigger mirror to increase the field of view. To me, a flip mirror with a central hole big enough to illuminate a 1 cm X 1 cm (~1/2 inch) chip would be ideal.

Thanks for checking them out guys.

dickbill, that's an interesting idea, a cassagrain OAG. :) I had similar problems with the Meade OAG, in some configurations it would only illuminate half the guide camera chip. The pickoff prism in this TeleskopService OAG/flip is quite a bit larger and fully adjustable. I can set the prism as close to the imaging chip as possible.

It's also 360 degrees rotatable independant of the camera but so far I haven't needed to 'search' for guide stars. Once or twice I've just needed to offset the target framing a bit to get a guide star. I left the piggyback refractor in place with a DSIpro on it so if some target is missing guide stars in the OAG I'll just switch to the refractor.

#11 Mike7Mak

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Posted 06 January 2013 - 03:30 PM

Looks like a nice, neat setup Mike!

Warren, it wasn't always so but I found through trial and error the Mak 7" works best with the reducer as close to the visual back as possible. The AP reducer is on the nosepiece up inside the microfocuser. I'm toying with the idea of ditching the microfocuser for one of those Baader clicklocks and going with a JMI motor on the mirror focus knob. I have a feeling I'll probably regret it 5 minutes after I do it though. For now I think I'll leave well enough alone. :)

#12 Peter in Reno

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Posted 06 January 2013 - 04:59 PM

I believe Mike can find guide stars easily with OAG because his guide camera uses a high sensitivity Sony Exview CCD. I believe this is the same CCD as Lodestar. Lodestar is famous for high sensitivity and great for OAG due to skinny 1.25" eyepiece style barrel. Lodestar allows to be inserted inside the OAG's guide port to bring Lodestar's CCD closer to the OAG's prism. The closer the guide camera to OAG's prism the better.

Peter

#13 Mike7Mak

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Posted 06 January 2013 - 11:44 PM

I don't know about same as the Lodestar but the DSIpro2 is a sensitive camera due mostly to its large-ish pixels I think.

This OAG only comes with a t-thread connection for the guide camera so to use a Lodestar you'd need to also buy a t to 1.25" adapter.

I agree the closer to the prism the better BUT that is entirely dependant on how close the imaging chip is to the prism. I got lucky, the Atik backfocus + the Xaygl filterwheel + a 5mm t-spacer (to keep the OAG thumbscrews from hitting the flat face of the filterwheel) puts the guide cam as close as it can get. In fact I need to replace the 5mm spacer with a 7.5mm one cuz the guide cam isn't quite in focus.

#14 zerro1

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Posted 06 January 2013 - 11:54 PM

Nice Work on these shots Mike! I've really been very happy using my Meade DSI's for guiding.

#15 Peter in Reno

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Posted 06 January 2013 - 11:55 PM

You can get T-Thread to C-mount adapter since Lodestar uses C-mount.

http://agenaastro.co...le-adapter.html

I looked up Meade DSI Pro II and found out that it uses the exact same Sony ICX429AL CCD as Lodestar. Large pixels may help but Sony Exview CCD technology is extremely sensitive. Exview CCD is already used in new Atik 460EX and SXVR-H694 cameras. These cameras are probably the most sensitive in the astronomy market.

Peter

#16 Mike7Mak

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Posted 07 January 2013 - 12:20 AM

Hi Robert thanks.

I looked up Meade DSI Pro II and found out that it uses the exact same Sony ICX429AL CCD as Lodestar.

Well ok that's 600 bucks I can spend on something else. :)

I liked my DSIpro2 a lot. If I'd found a way to seal the ccd chamber so the Outback cooler didn't dew up the chip I would probably still be using it for imaging. (But maybe not, the slightly larger chip in the 314L is kinda nice.) :)

#17 Peter in Reno

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Posted 07 January 2013 - 12:45 AM

I didn't mean to suggest to get a Lodestar. You already have a high sensitivity guide camera which helps to easily find guide stars with OAG.

Peter

#18 Mike7Mak

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Posted 07 January 2013 - 01:04 AM

I didn't mean to suggest to get a Lodestar.


Lol, no no no. I know you didn't, I was just making a joke. I have a tendency to spend money on things I really don't 'need' if I get it in my head they're even a little bit better. Like this new OAG for instance.






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