bobro

The Astromaster RA drive mentioned above does not have accurate speed control - it has a simple DC motor with a difficult to use speed adjustment. This isn't an issue for visual, but for imaging (assuming you are able to fiddle with the control to get a reasonably accurate speed) star trailing in images will occur due to motor speed inaccuracy/variation - you may be lucky enough to get 30 secs before trailing starts with your 150P (I managed 30 secs much of the time with my Meade 130/650 using the simple RA motor). I'm familiar with the design, having reverse engineered the circuit to modify 2 motors for dual axis guiding for my EQ2 - in that case the speed accuracy wasn't important as the guiding setup varied the motor speed in RA as required. The EQ3 motor mentioned above is an accurate motor drive - hence it doesn't need a speed adjustment. This motor is suitable for astrophotography and will allow longer exposures that make for better astro images, though the lack of goto may become an annoyance, so an improved solution could be to fit a SynScan Upgrade kit at £285 if funds allow.

These 2 youtube videos may help: https://www.youtube.com/watch?v=Ps8d4P7fWK0 https://www.youtube.com/watch?v=xlGF7PYLpYE

I'm not 100% certain, but I recall the EQ1 and EQ2 having different gearing. That's not really an issue with the adjustable simple motor, so the physical attachment is what is important there. For a precision motor both the gearing and physical attachment are important : assuming that EQ2 gearing is correct for your mount, it will need to work mechanically with your mount. Although EQ1/EQ2 mounts (especially SkyWatcher, Celestron and Meade) sell in numbers, yours looks to be an older mount design that may be different from what is sold today.

The basic/economy motors are just simple DC geared motors with a (tiny) control to vary the speed. When the basic motor starts it tends to run a little fast before settling down. Once the control is set to the correct speed it will track the sky reasonably well - when I started out with imaging my EQ2 Economy motor would allow 30 sec exposures with a 650/130 scope before drift became visible. For visual this is obviously not critical. Setting the speed is a little tricky with the tiny control. A disadvantage is the loss of the slow motion control. The range of speed setting is large. The motor with a handset provides precise speed control - it most likely has a stepper motor internally. The correct motor for the mount gearing must be used as there is no adjustment. The motor clutch allows the slow motion control to be retained. I still have my EQ2 (Meade type) and can help with a comparison if that helps. Bob

Thinking back to last night's imaging session, PHD2's guiding graph was bad with 'spiky' movements in both RA and DEC. Normally guiding is much better than that and DEC will show as very stable on the graph. As I was imaging high in the sky, for the very first time I used a dew heater band wrapped around the lens of the Orion 50mm guidescope to save me from continually wiping dew from the lens. Could the dew heater have caused the apparent poor guiding? (Images weren't great either.) If so, any tips on using one? Thanks

Great explanation from @vlaiv - first time I have understood the reason for taking bias frames.

That's showing more colour. It looks as though flats haven't been used in stacking. Using flats really helps with targets having gradual variation in brightness as the true variation comes through. Any chance of adding flats if they have not not already been added?

Kappa Sigma stacking works really well (as you already use) in eliminating satellite and plane trails as it works at the pixel level.

That's a very good image with really good detail (much better than I have ever achieved). It's not a big deal but the trailing stars towards the right hand side of the image looks to be due to polar alignment not being accurate as the trails rotate about a point. An earlier post by yourself shows you asked how to best use a polar scope, though without response. I can't help there as I use Sharpcap for polar alignment (very good), but you could try searching the forum (no doubt has been asked numerous times before) or posting again. Great work.

For my 2nd attempt at LRGB imaging I tried the Eastern Veil nebula, capturing (2 min subs) 2.5 hours of L and 40min each of RGB. My attempts at processing only produced noisy images that were not sharp - I wondered what was wrong. Last night was clear (much better than recent nights it seems) - 1 hour of Blue only capture plus better darks produced a much cleaner and sharper Blue image with much less noise than before. So, after a bit of comparison, I scrapped the previous 2.5 hours of L and most of the previous Blue subs, leaving 1 Hour of Blue and 40 min each of the previous Red and Green to try and put together an image. The resulting image has a different colour balance in the lower right corner in particular - perhaps down to the less than clear skies for the Red and Green capture? Seems a very blue image, so must need some re-balancing. At least something came out of it - especially realising there's no substitute for dark clear skies!

Me too! I tried Startools but got a bit lost.....

Nice image with round stars, though it looks like the black has been clipped as the background is very black, resulting in a loss of some faint detail. The attached quick process of your image (hope you don't mind) with some stretching and saturation increase starts to show some of the potential detail. Perhaps you could have another go at processing to bring out more detail, keeping the background not so black?

The setup requires 2 separate camera apps: guiding and image capture. PHD2 provides guiding and will be connected to the ASI120 and the mount guiding interface. ASIcap provides imaging (haven't used it) and will be connected to the ASI1600. So you will need both a guiding and an imaging app running at the same time on the computer.

Thanks - I get the same result as you. As @wimvb says, the lack of darks will be a problem, especially as a narrowband image of 180sec subs will need a good deal of stretching. For a quick test, below are 2 images from the session I did last night. The filter used was just a red filter with 120sec subs, so the amount of stretching required is less than for narrowband. Nevertheless, the sensor amp-glow (IMX183 sensor) is clear in the first image without darks (2nd image has darks added). The ASI1600 sensor has a different and less distinctive amp-glow pattern. This link has details : https://astronomy-imaging-camera.com/tutorials/what-is-amp-glow.html

You've done really well getting to grips with what isn't the simplest setup to start with. Next step is to have fun using it and learning from it!

One way is to 'Enable Server' under the Tools menu in PHD. APT then is set to use PHD as the guiding program (F7) sending guiding commands via PHD.

Looks almost as if the flats have been applied twice. To get feedback it helps if a single unprocessed sub is posted, plus the master flat.

For nebulae: M8 and the smaller M20 could be worth a try as they should peak at 45 degrees elevation (M81 will be very low in the sky from Hong Kong).

My first attempt at LRGB showed up issues with the scope (modified Meade Polaris 130) https://stargazerslounge.com/topic/336197-first-lrgb-attempt-m101-with-183m/?tab=comments#comment-3658963 So I decided to beef up the focuser by fitting a metal plate and adding another couple of teflon strips inside the focus tube to better hold the focuser. I couldn't get collimation quite correct so purchased a laser collimator (had to collimate the collimator first as it was miles out!). With the (hopefully) improved scope last night, although windy, was clear for a test. 1 hour on the Veil nebula with Altair 183M. Just a bit of stretching on the image - star shapes are unaltered. I can't wait to add a bit of colour (and a bit more luminance too).

Thanks! Here it is - for better or worse!

Looks really good to me - nice depth in the brighter parts and especially the view showing the central part of the nebula as I've only managed to image that part as noise so far. Your long exposure has worked well. Although my post processing skills are limited, I couldn't resist a bit of brightening and (as it looks a little green on my laptop) some colour balancing at bottom left using GIMP. If it's ok with you, I would like to post it.

Of course - that's stacking with pixel rejection, which further reduces apparent noise and is also useful in removing satellite and aircraft trails. A bit of magic!

My SkyWatcher 150PL scope rings take 1/4" UNC. The bolt looks similar to an M6 but has a slightly larger diameter and a different thread. The photo shows a standard 1/4" camera screw correctly screwed into the tube ring. An M6 bolt won't go in due to the different thread. Perhaps you can find an ebay seller that does them if you don't wish to order from FLO. Here is a link to a discussion some time ago: https://stargazerslounge.com/topic/16317-skywatcher-thread-size/ Certainly a confusing issue!

1/4" UNC is correct. Same as camera tripod.

Although darks are intended to reduce pattern noise, a master dark will add some noise to each target sub before it stacked. A sufficient number of stacked darks will reduce the added noise - hopefully to a low level. However, whether the amount of noise added is significant depends on such things as the target signal strength (brightness) and the noise level of the camera. Narrowband imaging reduces the target signal and DSLRs typically have higher noise than dedicated astrophotography cameras. The aim with longer overall exposure time is to further reduce random noise in the final image. If an insufficient number of calibration frames have been taken, the calibration frames could end up introducing so much noise that the benefit of longer overall imaging time is lost. The overall exposure time is typically made up of stacked subs. It's not the stacking that reduces the noise, it's the length of the overall exposure - stacking is just a convenient method of increasing overall exposure time. I don't have much experience with using darks (I used dithering as noise reduction with my DSLR) - perhaps someone else can suggest rules of thumb or a way of determining how many to take, especially with narrowband? However, as a general finding, stacked exposures start to become smoother once about 25-30 subs have been taken and stacked. You have done really well with the Ha image. I briefly tried Ha with my Canon 1000D but didn't go further due to the long exposure times required and noise in subs.