Adam J

I think that the current crop have moved to a different thermal pad. So hopefully its fixed going forward.

A top draw image mate, one of the best of this subject I have seen, very good effort. Beautiful colour handeling / processing. Original version for me though. Adam

Its nothing to worry about thats normal stepper motor noise.

Yes terrible behaviour. No skin off his back to sort it on ops behalf even if he refuses the refund.

I could be wrong olly but I think there is a forum rule on naming and shaming? Adam

Out of interest was this astrobuysell you got the camera from? Did you pay via paypal? If paypal and not friends and family then you can contact paypal. Adam

Point out to him that this is a known fault that ZWO will sort out for him but that it has to be him that sorts it as they will not deal with a second hand user.

Contact them and send it back for refund they need to sort this out before selling it on. Its oil from the thermal pad that has leaked onto the sensor. It will keep spreading until its over the sensor and then cause lots of pain. Adam

Best thing to do is to take a look on astrobin for images taken with it. Look at star quality and field flatness as opposed to the objects in the image as that is more a processing thing. I have not heard many bad things about it, its similar to the version offered by FLO in the UK. Most images with that scope I have seen look good, only seen one potential bad one that looked to suffer form miss centred lens elements, but none of these mass market scopes are fully risk free. Adam

Looks like one of the TS 70mm F6 doublets from about 5 years or so back. Probably a FPL-51 model, but thats a guess, do you know the aperture at least?

Yea there is no way its fallen here, if anything its gone up by a massive amount. The sky glows white now and every single retail and industrial site in the city has poorly fitted white lite LEDs. It that is not enough on its own then we are also seeing every man and his dog getting those wall lights that point straight up on there house and leaving them on all night long. What might have caused the result is less cars on the road as headlights do make a contribution to light pollution. Adam

I would and do use one irrespective of camera when guiding.

Odd choice as I consider zero backlash of a harmonic drive driven Dec to be one big advantage. So this is basically saving money and allowing no counterweight imaging by removing one harmonic drive. But it's not significantly cheaper than the ZWO. So not sure hot to feel about this one. Edit, just noticed its 1kg lighter than the ZWO so that is nice. Adam

No I would not use 120 gain on this camera, it will cause you calibration issues. There was a recent thread about this that I will try to find for you but essentially the camera has a none linear responce below ~190 gain and it causes problems, it also saturates at less than full well. Essentially use gain 200 especially for narrowband, but also for LRGB. Adam

looks like an issue with star masking at some point during the processing to me, you probably did it without realising. Adam

That behaviour suggests that the voltage is dropping as the cooler uses more current and causes the camera to trip out. Maybe take a look at the input voltage when running the camera at max cooling. Adam

Dont know if you got this sorted but if not then may I take a look at the centre of the field? Adam

I would save your cash and adjust collimation yourself. Just purchase the cheap artificial star from FLO and make sure you are getting concentric diffraction rings either side of focus in the centre of the image. If not then tweak the main collimation screws (not to be confused with the centring screws!) until they are concentric.

This is exactly why I really disagreed with the change in policy allowing people to sell items on this forum without gaining reputation first. But I suppose that I can and do look at post count when I buy from someone on here. Adam

I don't know Steve its happened to me a couple of times, someone on ABS literally sold me a filter wheel with a obviously stripped thread on it and I have received a scratched filter, again ABS. In both those cases the sellers refunded. But recently I came to the conclusion that I wont ever buy an expensive item like a mount, scope, or camera without seeing it working first. My biggest one i fear is buying optics and they are hit and miss new let alone second hand, the scope itself can look great and be utter trash, there is just no way to test it at a motorway service station meetup on the M1. Adam

No but they do ban people for selling broken kit. Adam

You really must report him to ABS they look very dimly on this type of behaviour and will ban him. Adam

Exactly this, they should take it back and return it to be fixed, terrible behaviour. Adam

Strehl is often quoted as the single measure of lens performance these days and unfortunately it's not the case. In fact in the case of imaging pit to valley is the more important reading alongside polychromatic strehl. It is very possible to have a 0.95 strehl lens that has greater than a 1/4 wave PTV and hence doesn't meet the strictest definition of detraction limited performance. Adam

Ok, here is the thing for me at least. I have seen optically horrible examples of every single scope that has so far been mentioned in this thread. To the extent that I would estimate a minimum of a 1/10 chance of getting a lemon no matter what scope make you chose unless you go for a premium brand like TEC, TAK, CFF, AP, LZOS or stellaview etc. But even then I have seen some bad examples, noting that I am quite demanding. So if you are wanting a scope with mass produced machine finished optics then my advice to you is as follows. Buy from a UK dealer with a known good returns policy. If one said dealer happend to be a bike ride from your house and has a good returns policy / excellent customer service, why look further? I am sure a GT81 will meet your needs just fine. Adam