blinky

Think I have it sorted now, and cmos means I can take shorter images so guiding does not have to be quite as good!

Thanks very much for all the information - Im going to create a dark library tonight, of 1,2,3,4,5,6,7 min subs - At least its just a one off exercise whilst its till light, I will stick them in my dark garage and shoot them tonight

Sorry, we both replied at the same time!  Can you look at my last reply and confirm its correct?  If so Im going to create a master dark and bias library tonight for gain 75 offset 60 and gain 200 offset 60 and just use those for LRGB and Narrowband

It's because my offset is 12!  So, I should increase my offset to 60 to avoid clipping and at gain 75 I should be aiming for around 1,300 ADU in 16bit - Simples!

5 hours ago, symmetal said:

Hi blinky,

 In your calculations you haven't used consistant units. Read noise is in electrons (e-) while your sky background is in ADUs (16 bit).

To convert read noise to ADU (12 bit for ASI1600) divide read noise by the gain in e- per ADU. So read noise in 12 bit ADUs:    2.25 / 2 = 1.125

Multiply this figure by 20 :    1.125 * 20 = 22.5

Add the offset which is in12 bit ADUs :    22.5 + 12 = 34.5

Convert 12 bit ADUs to 16 bit ADUs by multiplying by 2 ^ 4 = 16 :     34.5 * 16 = 552

So your sky backbround ADU is 552 to achieve a  20 * Read Noise figure. Your current ADU figure of 368 is lower so you need to increase the exposure duration to reach 552.

In this thread there is some useful info, and at the end I included an excel spreadsheet to calculate the sky background ADUs for various read noise swamping calculations.

The offsets recommended by Zwo are too low and do cause black clipping.

I would just start at unity gain for everything until you get more familiar with the camera as any benefits/disadvantages with different gain settings can be quite small and taking many subs will be your best way of getting the best image. I use gain 139, offset 56 (to avoid black clipping) for everything. Another advantage of just using one gain setting is less sets of darks needed. 

Alan

Thanks for that, I’m still confused though, how come the excel spreadsheet shows 1283 for your sky background at gain 76?

Hi,  

Just ordered one of these but am a bit concerned it wont fit my scope - it seems that the height of the unit cant be adjusted and Im worried it wont fit my Steel Track focuser.

1 minute ago, geordie85 said:

I prefer the first one. The 2nd seems to be clipped, but that may just be my phone screen

I always find setting the background to be the hardest thing to get right!  On my screen it looks OK but im not sure which version I prefer

Never had time to get the other narrow bands so this will do for now!  68X2min subs from my F4 Newt and ASI1600 - pleased to see the outer core was starting to come through in 2 min subs, not sure if I should have had more or went for longer to bring them out?

Quote

Yeah thanks - watched that and its really interesting but a shame he never had time to go through the gain and offset settings!

Pixinsight histogram

Hi,

Im trying to figure out what settings to use for RGB and Narrowband on my ASI1600 - there are a few interesting but confusing posts on CloudyNights about this but I cant figure out what to do!  I have a red filter, offset 12, gain 75 image, exposed for 60 seconds. The scope was an 8" F4 Newt and my skies are pretty good, I can just about see the milky way so not fantastic but Im about 5 miles outside Edinburgh in a smallish village.  So.….I should be aiming for about 20x the read noise for the sky background yeah?  So, the read noise, when looking at the graph in the manual, for gain 75 looks to be about 2.25, so multiply that by 20 and you get 45.  So is 45 the magic number I should be aiming for in the Median of the image stats in SGPro?  If so then Im way overexposing as my median is 368.  

The other thing though is offset, I think its too low in this image as when looking in Pixinsight the histogram looks black clipped....

And finally, am  I best just to image at gain 75, or do people use different gain depending on filter?  I was using gain 300 for the Ha filter the other night and going with 2min subs.

So:
Should I drop my exposure time down lower till I get to 45 for the background?

Should I increase the offset?

Should I stick with Gain 75 for all filters or increase it for narrowband?

ngc7662_60sec_1x1_r_Red_offset_12_gain_75.fit

Interesting, I was using a different ga8n/offset for narrowband than rob, you dont this is necessary? 

Hi,

if if I click the gps button in eqmod and pick up coords then click accept is that all I need to do? Do I also then, once the gas screen closes, click set on the main eqmod screen?

Excellent, thanks folks

Hi,

Can somebody confirm the figures in the screenshot are correct for an ZWO ASI1600 Mono?  I want the gain set to 300 here as I want SGPro to use that gain for focus runs - I will set the gain/offset in each sequence, but why does the settings screen shown not have a section for Offset?

Levels in Photoshop (or whatever app you use) - you want to adjust the black level so its inline with the start of the histogram

Thanks folks, looks like I will stick with my current setup for now then. As I just paid for an SGPro license I want to keep using it for a while at least.

I am quite excited by the specs of the new Pi4 but having just invested in buying and learning SGPro I dont want to dump it. Is there any way to have sgpro connect in a client / server fashion to a Pi4 and still retain all its functions?

One thing you can do is get a magnifying glass and look at the tops of the components,usually a blown transistor etc will be a lot more obvious through a magnifying glass. Look for a little crater in the top! Also if it were me I would contact modern astro and enquire about a new board. I bought one for me heq5 and it was just over £100, I assume an eq6 would be cheaper.

Apparently usb 3 also has usb 2 cables or something so plugging usb 2 stuff in means you still get usb 3 speeds from devices that support that speed and usb 2 speed if the device connected only supports usb 2. So go for whatever suits best as it should not make a difference.

Cool, that was more or less the answer I was looking for!  Thanks for confirming

I got a William Optics ZS73 a few months ago and now only getting round to use it due to the weather! Anyway, I noticed last night that I can see the lens cell supports as shadows round stars, is this normal or should I ask for a replacement?

Interesting thread! I have never done anything to pixinsight but now I’m getting a new lapto with an i7 desktop processor and 32gb of ram I’m intending on tweaking things to get it as fast and user friendly as possible.....

Silly question but as somebody who has only ever used skywatcher what's the equivalent version to the eq6? Also I assume these can be controlled from a PC,but I take it you dont use eqmod,is there an ascom driver?