Peter Reader

First night out with my new-to-me Zenithstar 73 and the 73A field flattener. 76 x 3 min I'm not hugely impressed witht he flattener, can anyone else put this performance into contect? Is this the best you can get with Zenithstar 73 in terms of flat field? Sensor is APS-C.

thanks for this, I'm going to take this as "reasonably good"...

Thanks for the info. How much for your hard case @jacko61 ? 😁

Just picked up this Zenithstar 73 second hand as my first wide field refractor (FL=430mm) to use with my Canon 1000D and complement my SW 200PDS (FL=900mm with coma corrector/reducer). I'm primarily into DSO imaging and due to funds it was important to me that I could share the remote PC (Melee Quieter 2) and guider (ZWO224MC on SW9x50 finderscope) between telescopes. So for anyone interested: the SkyWatcher finder bracket will just about fit in the William Optics handle (it looks a bit rubbish but is at least solid). Pixel size of guide cam 3.75 um Pixel size of main cam 5.71 um Focal length guide scope 180 mm Focal length main scope 430 mm Resolution guide scope 4.3 arc-seconds/pixel Resolution main scope 2.7 arc-seconds/pixel Imaging / guiding ratio 1.6 Sensor width guide cam 4.9 mm Sensor width main cam 22.2 mm FOV guide cam 94.2 arc-min FOV main cam 178.6 arc-min Question for experts: I have the Zenithstar 73 tube rings quite close together so the dew shield can retract and allow the scope to fit in the case. The tube rings therefore do not straddle the Declination axis - any issues with this?

73 x 3 min lights (3 hrs 39 min total integration time) plus flats, dark flats and bias (30 each). Background processed with astroflat pro. Recently purchased a laser collimator which has been collimated itself and keen to know what you think of the star shapes. Guide log suggests <0.6 arc sec RMS and HFR typically 2.7 at 900mm focal length.

Hi all, 3 hours of 3 min subs on each target with (new to me) SW 200PDS. Is the streak in the pinwheel an internal reflection perhaps?

I used DSS and dumped all files into the same group. Because of the meridian flip and my lack of rotator, the images taken after flip are rotated by 180 degrees. I tried stacking all the same images in ASI studio and got a good result... Maybe a bit of defocusing after the flip presumeably due to focuser droop but not huge...

I've had this error when EQmod pulse guiding was set too low. Try 0.9

Hi all, Please see attached image comparing results of stacking subs before or after meridian flip versus all subs together. Can anyone comment on why this happens and how I might fix it? Many thanks

Hi guys, I've been struggling to center the secondary mirror on my (new to me) SW 200PDS. It seems different to my standard 200P. Don't suppose anyone near Oxford owns a 200PDS and can let me have a look for comparison? Much appreciated

Very informative, thank you. I also have the spider out at the moment and can see the spring is fully compressed yet there is a few mm available before the holder hits the spider... will cut the spring and see how it looks. As you say it will be close...

Very kind of you to offer. I'd be very interested to meet and compare. I take it your 200PDS is performing well?

Is the offset spider or focuser holes likely? Are Skywatcher scopes known to be assembled with this sort of variation? I would have thought a robot drilled these so they would always be in a consistent position. Will check for play as you suggest but I need like 2-3mm I think which is a lot...

I was under the impression that even offset mirrors should appear round and central under the focus tube...?

My issue is that even with all 3 bolts fully loosened and the central screw fully tightened, the secondary will move no further away from the primmary...

Setting up a Skywatcher 200PDS and concerned about secondary mirror position under focus tube (see image). Through sight tube it seems the secondary is too close to the primary (needs to move left in the image), however the central screw for the secondary mirror holder is tightened all the way in and there is no more travel. Can anyone advise?

How did we identify this rather than thinking its just 2 very close stars?

Using my remote setup now at every opportunity and leaving telescope out overnight runing NINA on a mini PC. Pinwheel: 113 x 3 or 4 min over 3 nights (6 hours) NGC 2403: 62 x 3 min NGC 4736: 70 x 3 min All calibrated with generic master flat, darkflat and bias I took recently (camera position barely changes on remote rig). Anyone know how I can fight the green cast on my images? I assume this is from the IDAS D2 light pollution filter.

I currently have bothRGB and Per Channel background callibration unchecked. Would you recommend?

Would you recommend median Kappaa-Sigma or the one you highlighted? Median seems to be working for me but the other one not so much...

Thanks for the suggestion, unfortunately this didn't seem to help at all...

Flats helped a lot, thanks.

Hi all, Managed to process a decent image of Pinwheel in the end (thanks to those who helped me). I notice some weird red, green and blue pixels in streaks that looks like some sort of artefact from stacking. Is this something I can only remove with dark frames? Is there any processing that can be done to remove? Raw stack attached Thanks, Pete Pinwheel DSS output autosave 32 bit.tif

Noticed that the flats are not good: since I used the same panel and exposure setting as I do when I normally have my light pollution filter on I think the flats are too bright... will try reprocessing without the flats I took...

Yes, please find them here: https://drive.google.com/drive/folders/13mJ3zgJo75LnBnkSNvxpc_QNNnOVPEMX?usp=sharing