symmetal

Hi Peter, As Hugh says, congratulations, you've done a good job there on getting it all working. Hope it remains problem free for your actual imaging sessions. Alan

This is the effect of 'Amp glow' on an ASI 1600 dark frame. It's heavily stretched to make it obvious but the raw ADU difference shows the magnitude between the centre and corners. Without calibrating using darks, when stretching the image during processing the corners would show noticeable brightening. Up to 60s the glow isn't too noticeable and you can get away without darks to some extent, but for longer exposures they are needed. CMOS cameras exhibit it as the sensor read-out electronics, amplifiers and multiple A/D converters etc. are all incorporated on the sensor chip itself so certain areas of the chip can become hotter than others causing 'Amplifier Glow'. By comparison CCD sensor chips have all their read-out circuitry and the single A/D converter on separate circuit boards so it's easier for all the sensor to be maintained at the same temperature all over. i don't have a similar length ASI071 dark to post for a direct comparison but it's nowhere as bad as the 1600. As you say you don't need to take darks every night, once a year or so is normally good enough. Just take a set for each exposure duration you're likely to use (to avoid using dark scaling which isn't as accurate.) I take them on nights when it's cloudy, (plenty to choose from ) as it's easier to get the right temperature. Alan

You could then try for -5 or -10C in the summer which would be reachable for most days. On the noise vs temperature graph shown on your last thread, at -15C the noise graph pretty much levels out so the benefit of cooling below that is not so much. I'd just leave the set point cooling at say -25C in the winter even if the ambient temperature goes below that just to save possibly having to take another set of darks at the cooler temperature. Alan

Yes, dithering is beneficial no matter what the camera. With CMOS cameras it would still be useful taking darks as well. With set point cooling they are more matched to your lights for proper calibration compared to your DSLR darks. The ASI071 doesn't exhibit very noticeable 'amp glow' like the ASI1600 but would still benefit from darks. A set of darks should be fine to use for a year or more before possibly needing to be redone, (if taken at the same temperature as your lights). I've noticed that my 071 only cools to about 30 degrees below ambient compared to my 1600 which can cool by 40 degrees. You'll just manage to reach about zero degrees at +30 ambient so for the moment use zero degrees for your set point cooling and take darks at this same temperature. In the winter you can cool to -15C or so which is better noise wise so another set of darks at that temperature would need to be taken. Alan

In the Control Panel Plate Solve tab set the maximum number of regions to search before it fails and then uses the blind solver. This is under the 'Scope Frame & Center Here' section which is really mislabelled as it's purely for platesolving. By default it's Max Regions which is around 3000 or so. Select 100 regions instead which is the minimum selectable. When it then initially plate solves with PlateSolve2, if it doesn't solve after searching 100 regions (takes 20 to 30 seconds) it will fail and then automatically run the Blind Solver. This value will override the Max regions that can also be set in the PlateSolve2 'Settings' button so don't bother setting it there. Just to add, when PlateSolve2 fails and it runs the blind solver it generally doesn't say it's doing this as it just continues saying Platesolving... but it does run the blind solver. Alan

Ah! That explains it. Looked at their website. I imagine it's a PTFE type ball material. Good luck with the Lesvedome alignment. Alan

I expect they are UNC screws being US made. Can you post a close-up picture looking straight down on the screw and spring lying next to the ruler as it will be easier to give you the right size then as we can measure the thread pitch. The thread diameter looks to be around 2.5 to 3mm so your drawing is a bit off. Alan

Coming along nicely there Peter. Glad you got the Hall effect sensor working okay after repositioning it. What's the skewed bearing doing below the flexible coupler? Alan

I bought an ASI071 to use with my RedCat-51 but haven't used it yet apart from a few test images. It's a14 bit camera unlike the 12 bit ASI1600 etc and also has a higher full well of 48600 e- compared to 20000 e- for the 1600. So gain settings with the 071 have less 'critical' effect on your images compared to the 1600. I would just start with the default unity gain of 90 and offset 65. The manual seems to indicate 94 as unity gain but that's not much difference. I did a bias test and the offset of 65 does avoid black clipping at unity gain so all's well there. You'll need an IR cut filter (standard Luminance UV/IR cut is fine) as all three bayer colour filters pass significant IR according to the transmission graph. I had to get a 2" one to fit the RedCat. For 'standard' EQ mounts the home position is whatever position the scope is in when you turn it on so just point the scopes north as normal. The puck will be 90 degrees out from before but the scope doesn't know that. With Eqmod etc you can set another position as the home position if you wish (ie. the location the scope is assumed to be pointing at when you turn it on) but the scope just works out your initial goto from this assumed home position. Plate solving and syncing will then make this assumed position more accurate. Alan

Hi boyandorion, There's no need to apologize as there was nothing wrong with your post and it contained useful information. Most of the time low power zener diodes are used as voltage references. That may be the case here too, perhaps for some other part of the circuit, but from trying to work out the circuit by following the visible board traces it's hard to see in this instance. If the zener is in parallel with R21 it could explain the odd readings across the zener as the 100 ohm resistor would upset the diode test. If Matthew confirms it is in parallel by using the continuity (buzzer) function of the multimeter (with power removed) then I believe it would work fine without the zener. Alan

Hi Matthew, The AX5510 8 pin IC below the zener is a boost converter, 5V in and up to 27V out. AX5510 datasheet. This typical application circuit from the data sheet may help but there is no zener shown connected to pins 6 and 7 as you have. L1 above is L21 in your circuit and D1 above is a schottky rectifier which looks to be the SS34 schottky rectifier below your L21, and not the similar D21 rectifier which is getting hot. R3 above is R21 (100R) in your circuit. It looks like the zener is in parallel with R21 (that's how it looks but the apparent track layout may be deceiving) and may be a protection diode in case the 5V rises or something but isn't used as a reference voltage as that's internal to the IC. The output voltage of the AX5510 is set by R2 and R8 above. The zener would have some numbers on it but they may be difficult to read and desoldering it will probably be necessary to find them. As it's cracked it has to come out anyway. The circuit would probably work without the zener but whether you want to power it with the zener removed is up to you. With the zener removed you can do a more valid diode test but at the moment it does look a suspect for your problem. Hopefully the cracked casing hasn't removed any letters/numbers printed on it. You'll need a magnifying glass to read them anyway. Alan

So your method with the dot pattern on an LCD screen seemed to give good results which is certainly easier than sticking ball bearings to a board. Less reflections to contend with too. I found after adjusting the tilt adjuster with my Flt98 with flattener that I'd get good round stars all over on one night, then the next night or even the next target they would be slightly elongated in some corners. I found it was just due to slight focus differences. If SGP autofocus gave me funny corner stars I just shift the focus position out by 10 steps. Not enough to change the HFR of the stars by any significant amount (sometimes it would report as slightly better) but the stars would then be be round all over. I'm not sure what weighting (if any) SGP autofocus gives to best overall average HFR values compared to just best anywhere, but it often ends up with it being focused in one corner rather than nearer the centre. Alan

Hi Matthew, The electrolytic could be faulty, but as you say without removing it from the circuit it's hard to say. For high power SMPSs you want Electrolytics with a low ESR (equivalent series resistance, high temperature operation (105 degrees) and suitable ripple current rating. Here's the data sheet for KYA capacitors to give you some info. However, as yours is a low power SMPS unit these features are not critical so as Julian says any 'recently made' Aluminium Electrolytic would be fine. Alan

Can't really say. I tried it indoors but there were too many reflections off the walls etc. to get a meaningful result. I tried it at the end of the garden but the scopes on the fixed pier couldn't get a view due to obstructions. I took the scopes off and had them on the ground looking at the board but it was such a pain trying to get it all lined up running back and forth many times, and the board blowing over in the wind, that I gave up. Getting a tilt adjuster for the scope let me adjust it reasonably quickly on real stars anyway so I never tried again with the board. Here's the board I made. I used 5mm ball bearings as they were cheap for a few hundred but I think larger balls might give a more pronounced bright spot. The matt black paint I used was more satin black (should have used blackboard paint) so created 'hot spots' of its own with a torch shining on it and the overall brightness of the background was still fairly high, and I think the many reflections tended to 'muddy' the overall results. I believe using fewer larger ball bearings and real matt black paint would have given a better result. Alan

+1 for what pete_l said. It's worth checking the diode D21 with your meter. It should measure higher resistance in one direction than the other (Reverse the meter leads). Your meter may have a diode check function anyway which can give useful info even though the diode is still connected to other components. Here's a Youtube video showing how to use the diode check function. As it's probably a schottky diode (low forward voltage drop) it would likely measure 0.2 to 0.3V. Also check the three large electrolytic capacitors by it for shorts (or low resistance value in both directions) using the resistance function on your meter. Alan

Looking good AbsolutelyN. As you're using the bracket with the counterweight attached you could get something like this to adapt the 3/8" thread on the bracket to the 1/4" for the Zwo camera to save using the second ballhead. Alan

your Zwo camera has a 1/4" mounting hole in the rear. You could find a suitable 1/4" bolt long enough bolt it to the dovetail through one of the holes or slots. The finderscope mounting rings and bracket aren't needed then. Then clamp the dovetail in the Star Adventurer. (Mount the camera towards one end of the dovetail so there is enough dovetail left to clamp to the SA). That should be sufficient for using sharpcap to polar align I believe. Alan

That's looking good NV. Alan

Hi NV, Glad to see it's all working again with the new motor. The movement looks like it's normal behaviour given the way the motor unit is attached. You could loosen the three screws holding the motor unit to the scope and see if there is some play in allowing it to move sideways. You may find a position where the oscillation is minimised. Very thin spacers under one or two of the screws would probably help too. As the oscillation is at a low speed it's not causing much harm so whether you want to try is up to you. Alan

Hi Mandy, I use the ASI178MM with my Lunt 60 Ha solar scope and with a focal length of 500mm the full disc just fits on the sensor. There are no Newton's Rings effects either which is good, although they are quite evident if I use a 2.5 x Powermate. The Powermate added no extra detail anyway as the 178 camera image scale without it is well matched to the Dawes limit of a 60mm aperture scope. Here's an image I took in May with the 178. Alan

Yes. you were correct. Just to confirm the sky b/g ADU at gain 75, offset 60 is 1347 using 10 x RN ^ 2 and 1312 using 20 * RN. At gain 200, offset 60, it's 1633 for 10 * RN ^ 2, and 1888 using 20 * RN. At higher offset values this becomes a more dominant factor so the sky b/g ADU differences are not so greatly influenced by gain or calculation method used. I'd use the 10 * RN ^2 values personally. The numbers are just figures to aim for. If your image sky b/g ADU is around those figures that's all you need to do. For RGB you can either have different exposures for each colour to achieve these figures, or choose 1 exposure for all three which is near enough not to make much difference. Luminance will be around 1/3 the RGB exposure duration. For narrowband it's unlikely you'll be able to expose long enough to achieve these sky b/g ADU figures unless you have bad light pollution. I generally choose 480 secs for Ha (at unity gain). In my bortle 3 skies I'd have to expose Ha for over an hour to achieve the 'recommended' ADU values. With you using 2 x unity gain a shorter exposure may be better (240 secs or so) allowing you to take more frames in the same overall time to overcome the loss of bit depth caused by using higher gain. It's commonly stated not to use bias with the 1600 as there are reports of some odd results, though personally my bias frames look 'normal' I just use the bias (or short exposure) to analyse the histogram to see if it's black clipping. When you do some LRGB test exposures to determine the optimum exposure time wait until at least an hour after astro dark so that the sky brightness is fairly constant. Then use these exposures for all your subs. If astro dark has just arrived you'll find these exposures will give a b/g ADU which is too high but after a while they will settle down to the 'right' value. If you create your dark library before knowing the correct exposure duration you may have a lot of unused darks, unless you use dark scaling. Good luck anyway. Alan

Those calculations are with offset 56. If you use offset 12 you have to subtract (56 - 12) * 16 = 672 from those figures. The 20 * RN then becomes 576 and the 10 x RN ^ becomes 611 ADU. I read the graph as the noise at gain 76 being 2.2e- while you read 2.25e- hence the slight difference in the calculated values. You deduced that just as I posted. Alan

That's looking good Dave. Very similar to mine after Es' gave it his attention. I bought an ASI071MC, APS-C sensor to use with the RedCat and Star Adventurer (there isn't a mono version) to hopefully avoid the DSLR colour mottling effects and have only done a few test frames so far. At 2 mins I have to throw away half the frames due to sausage stars. I'll have to try for a better alignment. I fitted a Zwo Mini-guide scope to it so can use the PHD2 drift align method which hopefully will help. Alan

When I started with the ASI1600 I too used 2 x unity gain for narrowband and 0.5 x unity for LRGB as often quoted as 'optimum' on CN forums. Too often I ended up forgetting to set the right gain as SGP has three places where you can set the gain and 2 for the offset, with different priorities. The SGP option for adding the gain and offset to the filename never seemed to work for me so had to manually put it in the 'suffix' field to know what the settings were (hopefully). Setting just one gain/offset in the Ascom driver only did away with the need for all this palaver. I use the 10 * RN ^ 2 setting for the sky background swamping level rather than the 20 * RN as that seems to be accepted as more 'realistic' and with my fixed gain/offset of 139/56 it's 1386 ADU for everything. Alan

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