M81 with Optec 0.5x reducer on C8 SCT

[Ikonnikov]

Being galaxy season I have hung up my Hyperstar and had a go with an Optec NextGEN WideField 0.5X reducer I bought some time ago for my C8. This works out at 0.75 arcseconds/pixel with my Atik 490EX, close to the limit of what I can guide on my HEQ-5 (and not helped by my dodgy seeing) but the results are a noticeably higher resolution than with Hyperstar.

It took me a while to get the spacing near correct and it’s still perhaps a little off or maybe there’s a slight tilt in the focal plane, but the central part of the field is starting to look ok. The flats were not quite right; so a couple of big bunnies at the edges haven’t been removed properly.

In total the image comprises 28x10min Luminance (IDAS LPS P2 filter 1x1) and ~20x 4 min R,G and B filters (behind the IDAS, binned 2x2). Guiding was with a celestron OAG and ASI120MM mono camera which seems to work well with the OAG with 2x2 binning enabled.

Paul

Full res at http://cdn.astrobin.com/images/thumbs/3a08125935ff90965dde764c7dd05fcd.1824x0_q100_watermark_watermark_opacity-10_watermark_position-6_watermark_text-Copyright%20Paul%20Cordell.jpg

[Astroboffin]

Fantastic result, if only I could......

AB

[toxic]

very nice 

[MikeD]

Nice, Ha regions showing up well through the IDAS.

Mike.

[Coco]

Superb, thats a fabulous image, no sign of a floppy mirror here..

[Ikonnikov]

Thanks guys for the positive responses.

Nice, Ha regions showing up well through the IDAS.

Mike.

Oops I forgot there was some Ha in there too (added to R and L) although it wasn't very much! A couple of hours I think and through a Baader High speed F2 filter so not really optimal for this setup. Too late to edit post.

[Chris]

Wonderful! That Optec reducer works very well by the looks of it, F/5 1000mm FL on a C8 sounds very handy for imaging. 

[strutsinaction]

Paul

Is that with a C8 EdgeHD or 'standard' C8?

Regards

John

[Ikonnikov]

Paul

Is that with a C8 EdgeHD or 'standard' C8?

Regards

John

Hi John,

It's a non-edge HD C8 I use (although Optec do a reducer for HD versions the NextGEN WideField 0.5X is for standard SCTs).

BW

Paul

[Coco]

Anychance of posting your PHD settings using the ASI120MM, do you use ascom or on camera?

[Ikonnikov]

Anychance of posting your PHD settings using the ASI120MM, do you use ascom or on camera?

Hi,  I use the ASI120 as a windows WDM-style webcam camera in PhD(2) along with the ASI ST4 ASCOM telescope driver for the mount as it easily allows you to change camera resolution and enable/disable binning. Once you connect camera you can choose the resolution from a list and the first instance of '640x480' is the 2x2 binned version giving 7.5 micron equivalent pixels (I assume the second instance is a cropped image with normal 1x1 3.75 micron pixels). You need to set the exposure every time you launch PhD2 in the camera settings (in WDM mode the PhD2 exposure setting just determines the length between the start of exposures  not their duration) but this is not a problem for me regarding darks as I always tend to use the same exposure with the OAG (3s). I know everyone raves about the lodestar but I've not had any issue finding a guidestar with this setup at 1000mm using the 2x2 binning mode and you don't have to deal non-square pixels (caused by mandatory 2x1 binning on the Lodestar) either. The ASI's (unbinned) small pixels also work very well with short FL lenses as guidescopes.

I've managed to overwrite the (PhD2) settings specific for the  C8/optec since putting a shorter FL scope on my mount but if I remember rightly  I had to reduce the RA agressiveness to about 70-75% to keep my HEQ5 from sawtoothing too much and calibration step was 1000 to 1500ms, everything else was at or near default though I may have had to tweak the minimum move setting a bit too initially.

BW

Paul

[Davey-T]

Very interesting Paul, I looked at the Optec reducers when they first appeared but apart from being expensive they had no UK supplier, still may not have for all I know.

I'm still using the usual 6.3 f/r and Atik 314L camera which works well having pixels maybe twice as big as the Atik 490 but .5X is appealing, been capturing some data on M63 recently and taken a few HA subs but haven't got round to processing yet.

Dave

[Coco]

Hi,  I use the ASI120 as a windows WDM-style webcam camera in PhD(2) along with the ASI ST4 ASCOM telescope driver for the mount as it easily allows you to change camera resolution and enable/disable binning. Once you connect camera you can choose the resolution from a list and the first instance of '640x480' is the 2x2 binned version giving 7.5 micron equivalent pixels (I assume the second instance is a cropped image with normal 1x1 3.75 micron pixels). You need to set the exposure every time you launch PhD2 in the camera settings (in WDM mode the PhD2 exposure setting just determines the length between the start of exposures  not their duration) but this is not a problem for me regarding darks as I always tend to use the same exposure with the OAG (3s). I know everyone raves about the lodestar but I've not had any issue finding a guidestar with this setup at 1000mm using the 2x2 binning mode and you don't have to deal non-square pixels (caused by mandatory 2x1 binning on the Lodestar) either. The ASI's (unbinned) small pixels also work very well with short FL lenses as guidescopes.

I've managed to overwrite the (PhD2) settings specific for the  C8/optec since putting a shorter FL scope on my mount but if I remember rightly  I had to reduce the RA agressiveness to about 70-75% to keep my HEQ5 from sawtoothing too much and calibration step was 1000 to 1500ms, everything else was at or near default though I may have had to tweak the minimum move setting a bit too initially.

BW

Paul

Thanks Paul, thats big help cheers..

[Coco]

Oh another quicky. Do you do anything with the cam dialog box?

[Coco]

Hi,  I use the ASI120 as a windows WDM-style webcam camera in PhD(2) along with the ASI ST4 ASCOM telescope driver for the mount as it easily allows you to change camera resolution and enable/disable binning. Once you connect camera you can choose the resolution from a list and the first instance of '640x480' is the 2x2 binned version giving 7.5 micron equivalent pixels (I assume the second instance is a cropped image with normal 1x1 3.75 micron pixels). You need to set the exposure every time you launch PhD2 in the camera settings (in WDM mode the PhD2 exposure setting just determines the length between the start of exposures  not their duration) but this is not a problem for me regarding darks as I always tend to use the same exposure with the OAG (3s). I know everyone raves about the lodestar but I've not had any issue finding a guidestar with this setup at 1000mm using the 2x2 binning mode and you don't have to deal non-square pixels (caused by mandatory 2x1 binning on the Lodestar) either. The ASI's (unbinned) small pixels also work very well with short FL lenses as guidescopes.

I've managed to overwrite the (PhD2) settings specific for the  C8/optec since putting a shorter FL scope on my mount but if I remember rightly  I had to reduce the RA agressiveness to about 70-75% to keep my HEQ5 from sawtoothing too much and calibration step was 1000 to 1500ms, everything else was at or near default though I may have had to tweak the minimum move setting a bit too initially.

BW

Paul

Thanks Paul, success at last, but my only concern now is that my snr is around 5 - 8 , ive double checked my guid scope focus ( M42 135mm and x2 teleconverter ) increased the duration in the 'camera settings' but best I have managed is snr 9.2 and it held on for only a short time, if the snr drops below 5  I get lost star warnings.. Ive all but given up using an OAG for these reasons..

[Ikonnikov]

Hi Guy, apologies for not replying sooner though I see you seem to be making progress . I often get guide stars with only 5 or 6 snr with the celstron OAG but PhD2 still seems to work ok with them most of the time. I think you can change the minimum acceptable  snr somewhere in the settings (star mass tolerance?) although I have not needed to so far. Increasing camera gain might also improve things (but again so far I have left this at default). Best of luck getting everything working properly.

Paul