Adam J

I know it wont make a difference to performance. So i guess this is more about value or perceived value. Hence you and me might be confident it wont matter but would a new astronomer looking for an ED80 be put off lol

it is visible to the naked eye under normal lighting. i guess it will bother some people more than others.

Just so long as its a pro model you really dont want the original model as it had some issues.

All, I am having a clear out and selling stuff I dont use to fund a mobile rig to use on an upcoming work trip to Australia. I have a SW ED80 DS-Pro that is not getting used as I use the 130PDS most often. (I dont want to start that debate here though please). Its got a small scratch about the size of a eye lash or a little smaller on the front surface of the objective. You cant really see it in pictures but here is one anyway. With flash. Nothing else of note visible without shining a torch directly on the optic and as we know that just makes you worry about nothing. This does not seem to effect its performance. I may take a image with it just to prove the point to a potential buyer. So my question is as OTA only whats it worth?? Difficult to find examples of scopes with scratches to get an idea or at least not that the sellers are admitting to! Was thinking its got to be worth £190 to someone? Thanks Adam

Don't discount a used Atik 460EX if the micro lensing is an issue for you, i think its a better sensor than the 183 unless you really want new.

The classic one is that if you have a ZWO guide camera (which i see you do) PHD2 can get confused and end up setting the gain of the ASI1600mm pro to the gain intended for the guide camera.

That is an odd looking flat for sure.

looks better without flats. So its miss-calibrated flats.

I would say thats a good choice but I would make sure it is compatable with EQ Mod.

Check out your offset setting too. I would say that 15min subs on a ASI1600mm pro are very long.... even in narrow band I only shoot 5mins at unity. Another possibility is that you had some high level cloud and it is just over exposed just to higher sky brightness. The fact that at lower exposure you see something but at poor S/N might support that theory. Shoot some Dark frames at the same settings, if they look normal for that length of exposure then I really doubt its the camera, if they white out then its the camera or firmware or settings. Adam

Its a tough one as the EQM-35 has larger diameter / higher quality gearing on RA (same as in the Star adventurer) but uses bushes as opposed to proper bearings, hence it should guide to a higher resolution than a EQ5 pro but at the same time it will not move as smoothly when balancing it. I have heard of people applying better quality lubrication to the bushes to get around this and acheive good results. In the end I would think that the EQM-35 will achieve better guiding than a EQ5pro as the EQ5pro is ultimately just a manual EQ mount with added drive motors. I would go with the EQM-35 and re-lubricate if required. Adam

Thats how I do it.

FOV looks too big for it to be the ASI178mm cool but I may be proved wrong when Rob replies.

As they say processing is 50% of the hobby. Its a steep learning curve for sure, but your already making improvements.

It will be great for dedicated galaxy imaging in very good seeing conditions. Clearly not suited to nebula imaging, you will of course need to guide the scope very accurately to in effect make your system seeing limited. Pixel scale of 1-2 is only for guidance. The camera will focus fine.

Yes although I have never tried to have the 12 volt cooler powered without the USB attached, I suspect that removing USB power would interrupt the cooling control.

I think the first thing is to understand the issue correctly myth or otherwise. As I understand it the problem is that every time the chip is powered it performs an internal calibration and so its not that the bias is unstable between images in a single run its that the bias is unstable between imaging sessions. As such you cant use bias from one session to scale darks from another session or vice versa because the bias component of the light frames will not be the same as the bias component of the dark / bias frames. Now the second issue is that this calibration is only applied at shorter exposures of less than a few seconds and so the bias component of the dark frames at 2 mins is not the same as the bias component of bias frame of 0.01 seconds. I have seen some people claiming that you can just use a 6 second bias frame as opposed to the normal minimum exposure hence avoiding the issue as the calibration will not be applied to darks or bias but have not tried this. In fact this is why its recommended to aim for longer flat frames with this sensor. The final nail on the coffin is that the amp glow does not grow in a linear fashion with time or at least that is what I am told, as such it will not scale anyway and prevents the use of dark frame optimisation as this relies on a linear model, hence why all the stacking programs tell you to turn off dark frame optimisation for CMOS in their manuals now to prevent residual amp glow. Finally there is something called telegraph noise in very short exposures (Horizontal banding that moves slightly / jumps between exposures) you will see it in a large stretch of a Bias but would not appear in frame stats as these are averaged across the frame. So although I don't have any raw data to hand I hope that this at least frames the issue correctly for you so that you can perform your own investigation. I note that none of the above conflicts with your result. Adam

Something may be shorting the pins on the USB connection, give them a clean.

It is present on all cameras that use the mono version of the Panasonic MN34230 CMOS sensor and that includes the ATIK Horizon and the ASI1600mm pro. It is the result of the glass that is glued to the front of the sensor itself by Panasonic not having an anti reflection coating and as such camera design has no bearing on the effect despite what some try to claim. The only thing that can make it more or less pronounced is the F-ratio of the optics with faster systems seeming to reduce the effect. It mainly shows up in narrow band due to the single frequency causing a coherent diffraction effect but will also show in LRGB to a lesser extent. Narrower Narrow band filters can help but only because they inherently attenuate bright stars more than wider filters making the pattern dimmer. The main culprits are Altinak and Gamma Cas and a few other stars of similar brightness close to well known targets. In the end of you point a ATIK 460EX at sirius and do a long expsoure you will get the same effect, its just much stronger and apparent on the panasonic sensor in comparison to others.

Yes that would cause the problem, retake dark flats and darks with the correct settings and I bet that you will see a big improvement.

If you used flats then you must calibrate them with Dark flats as opposed to bias or they will over correct on CMOS chips, giving this type of effect. Don't use Bias at all with CMOS.

Firstly you are welcome. Have you used flat frames? I would say that you have got either over correcting flats or the darks at different settings to the lights are causing you issues. You really do need everything at perfectly matched settings.

Depends on what your priorities are... For example I always tell people that if you are considering the ASI1600mm pro then you need to consider the Micro lens Diffraction problem and decide on if you are willing to put up with that in exchange for the benefits of a larger chip and lower read noise. Some people are some people are not. If the answer is that you are not willing to put up with it then the ASI183mm pro is an option or another brand with IMX183 or a second hand Atik460EX mono is always a reliable camera. In any case you will not need more than 1.25 inch filters with the SW80ED if you think you will image at F4 or lower at some point in the future then you might consider 31mm filters. In any case I would go Baader over ZWO for filters and that means avoiding the ZWO deals. The Baader filters are just optically better. Adam

The IMX071 and most sensors designed for DSLR cameras don't have amp glow. In general it's the machine vision chips that give the amp glow as the are not intended for long exposures by design.

I am shocked to hear you say that. What type of issues are you having? It should walk all over a 40D.