james_screech

I recently bought a second hand BRESSER Messier MC-100/1400 OTA. When the focuser is adjusted stars move significantly in the field of view, perhaps 0.5 degree per turn of the focuser knob. I assume there is a problem with the focuser not moving the mirror linearly in the tube but tilting it as it moves. This is born out as at times stars become comet shaped, implying that collimation is changing with focus setting. Is it possible to dismantle the OTA and improve the way the mirror moves (re-grease)? I've searched online but cannot find anything myself. Any suggestions would be appreciate

I could try dimming the panel, I already have an opal acrylic sheet diffuser.

No, the same with the observatory closed at night and no lights on in the observatory.

I've tried rotating the panel and this had no noticeable affect on the gradient, I've also subtracted one master flat from another and I get a gaussian distribution of noise cantered around 0. So I think the panel is fine. I might just have to go back to using a tracing panel (similar to yours) with the scope pointing straight up instead of horizonal. I can only assume something in the image train is moving but I can't figure out what as I can't feel any movement when I put pressure on the camera. The gradient is dark in the bottom left of the image and brightest in the top right (3%-4% d

Thanks for the information. However that's not my problem then as my exposure is less than 1 sec.

Nice writeup, you mention that the ASI1600MM-C give gradients on longer exposure flats, that's exactly the problem I've trying to solve for weeks since mounting a EL flat panel on the wall of my new observatory. Do you know what exposure is needed to avoid the gradients?

Teamviewer did the same for me, I filled out there non-commercial use form and after a few weeks it started working again, 4 months later it stopped again. So I now use TightVNC.

Something a bit different but still using a CCD/CMOS/DSLR camera, photometry of a variable star. Possibly a time series or an eclipsing binary, or short period pulsating star.

Can some one recommend windows software for an all sky camera. Ideally something that will run on XP as I was hoping to use my old ASI120MM / XP netbook for an all sky camera. Though I do have a spare Win7 netbook I could use instead. I'm aware of AllSkEye (doesn't support XP though ). James

Is there any free small application that can be used to measure FWHM / HFD from fits / DSLR images. Thank you James

Comet C/2020 F3 NEOWISE, Canon 7D Tamron 150-600 at 150mm, f5, ISO800 on a fixed tripod.

I'm currently having dealings with ShedShesSheds, I'm have a fold down roof observatory built by them, should have it in a few weeks. If you contact them use the mobile number as they tent not to respond to email, and one of the land lines (the one you need) on their website is wrong. James

200mm Newtonian with dual speed focuser, 28mm 2” eyepiece & red dot finder, usual marks on the dovetail bar and a few marks on the outside of the OTA nothing to effect the optics. USB powered cooling fan added to the main mirror also a brass compression ring eyepiece holder replacing the original screw type (original included as well). Complete with Sky Watcher 0.9 coma corrector, a laser collimator and Bahtinov mask. Collection only from Bedford £300.

My budget is up to £250.

I have a set of oldish ZWO LRGB filters, I just used eXcalibrator to estimate their colour balance ratios with my Atik414ex to try and improve my colour balance. I was very surprised at the results, which explain my problems with getting colour balance looking natural: R: 1.00 G: 2.07 B: 2.44 Green and blue need more than twice the exposure of the red! Can anyone recommend a filter set which will give a better colour balance for both my Atik414ex and ASI1600MM. I know ZWO have a set that are balanced for the 1600. Are they likely to be any good with the Atik as well or would