Jammy

Thanks for all the replies. I forgot about the optical length. Nothing is ever simple!

I've recently bought a Skywatcher telescope that came with a straight through 9 x 50 finderscope. Rather than buy a new right-angle version of the same scope does anyone know if you can just buy the right angle part? Seems odd to me that you have to buy a whole new finderscope. I'm not being tight, just doing my bit to save the planet! ?

I've recently bought an ED80 and ASI 1600mm Pro. I'm still getting used to the change after using a dslr for years. What gain level are you using? The detail has come out really well in your image. The halos don't actually look that bad - in a way it gives depth to the image. Ha filter is going to be my next investment. I'm trying to decide which filters to buy - cost is always the deciding factor! I already own the beginners Baader LRGB filter set, which seems OK so far. The LGB are pretty much parfocal but the R is a little off. I've read both good and bad things about the ZWO filters. I think the filters have been improved recently, although not entirely sure. I've give this a go with the LRGB tonight. If I get anything as good as yours I'll be happy.

Thanks guys, I'll take a look. You've been really helpful ?

Thanks for all the replies guys. I managed to make the flat frames light box at the weekend. I used @Oddsocks method for testing the light distribution, which really helped spacing the perspex sheets. I also needed to add some inner foam board to diffuse the light because of a slight light drop off at the very corners of the box. I probably wouldn't have spotted this without the photometer, to the naked eye it did look very even. I also did a stretch in photoshop as described by @Horwig. That idea came to me after I'd glued it all together, and before I read your reply! I've sized the front circle large enough to fit over the front of the C9.25, and I've also made an insert that will allow me to use it with an Evostar 80ED. I'm now waiting for a dimmer switch to arrive that I found on eBay, then I'll be ready to start taking flats. First time I've used foam board, surprised just how strong it is ?

I'm going to make something like this photo (image stolen from Richard McDonald's website). Foam board doesn't take screws very well (if at all), but can be jointed with a hot glue gun. It's the distances between the inner baffles that I'm trying to space correctly before I fix it all together.

Looks good Dave. I'm hoping to make mine compatible with my Evostar ED80 too by allowing a sleeve to fit within the opening for the C9.25 I'll post a pic when I'm done ?

@symmetal @Oddsocks Many many thanks for the detailed solutions. You've excelled yourselves ? I'm going to construct the box this weekend. Fingers crossed it will all work as planned. I've drawn a CAD model of what it will hopefully look like. Now to put the theory into practice! I'll give feedback when I'm done, but only positive ?

I'm making a flat frame light box for use with my C9.25 SCT using the traditional method of light behind opaque perspex sheets, and set within a foam board box. Large EL panels just feel too expensive at this moment in time. In order to make sure I've spaced the perspex correctly before I glue everything together, is there a way of checking how even the illumination of my flat frames are? I've seen on forums where people have posted flat frames with numbers, contours etc to show how even the illumination is, but I've no idea where these things are done. Do I need specialist software to do this? Thanks for any help

Would you say it picks up just as many stars as the QHY5L-ii did?

ZWO ASI120 mini or ZWO ASI290 mini as a replacement? I know the loadstar is probably best, but a bit pricey.

I was wondering if there had been a voltage issue for it to suddenly stop rather than the cable connection. Either way it looks like more expense.

I've plugged my QHY5L-ii mono guide camera into the USB2 hub on my new ZWO ASI 1600mm, and this worked a couple of times to for daytime focusing to get the distances right on my OAG. I tried again today and unfortunately the guide cam has stopped working. It worked briefly, then windows said that it had lost connection. The red light has gone out. I've tried reinstalling the native and ASCOM drivers, but nothing works. I've tried connecting directly to two different PC's with different cables and windows doesn't recognize that anything is attached to the USB. No light on the camera, so assume it's died. I've seen another post on Cloudy Nights where someone has done the same thing connecting this guide cam through the USB hub on the ZWO camera and their QHY5L-ii also died. Anyone else had this issue, or read similar anywhere? Wish I'd read that forum post before hand!!

I've now made a spacer from the lid of a margarine tub. It measures 0.45mm thick and works perfectly.

Thanks for the reply. I'll give it a try, I just thought the prism looked like it was going to be in the way of the sensor. The manuals always make everything look perfectly orientated!!