symmetal

36 minutes ago, dan_adi said:

So, making  pinhole in the cover lens won't work

No, as well as having a large depth of field as Michael said, the depth of focus on the sensor will also be large so changing focus will have little visual effect. Pinhole cameras are the extreme example of a stopped down lens so any image will be very soft anyway due to diffraction effects.

Alan

Glad it helped. For some useful tips on getting the best framerate and pictures etc the posts I made in this topic should help. They refer to Firecapture which I normally use but would apply to SharpCap or similar programs too.

You can do fps tests just with the camera alone plugged in to the PC. No need to have an actual picture. You can vary the ROI and other camera settings to see how it affects the frame rate, and how long a video you can record before your PC runs out of RAM, when the frame rate will likely drop off, though if using a SSD disk this may not be significant. Firecapture displays how much free RAM is left as you're recording.  

The ASI2600 is not designed  for use as a planetary type camera, so the fps you achieve will be less than a dedicated planetary camera like an ASI224MC, ASI178MC, or any newer models. A cooled camera also isn't required for planetary work.

If you have the free Stellarium planetarium software installed you can input the details of you scope and camera and have it display the FOV you'll get . If you select the Sun as a target you can see what a suitable ROI is needed to see the corona features without capturing too much background sky which would reduce your framerate.

While the video is being recorded you can vary the exposure with the exposure slider, and the preview image and histogram will display the image live so you can change it as you wish. The stacked image of each recorded video segment will show the average of the exposure during that segment, which shouldn't be a problem.

Just to check I assume you're using a dedicated solar filter on your scope. What scope will you be using by the way? Smallish refractors are the norm for solar, though others are fine if you take the necessary precautions with regard to filtering.

Alan

Hi Michael,

For imaging the Sun or Moon it's better to take a video of the whole event with your ASI2600MC using a program like Firecapture or Sharpcap. The length of the video is dependant on how much ram and storage space you have available, preferably a SSD drive. Selecting a region of interest on your camera just large enough to capture the image area you want you can get a higher fps from the camera.

Then using the program PIPP you can split the long video into like 5 second segments and then stack each segment in Autostakkert to give a final composite image which will be higher quality than a single video frame. If you want more images you can split the video into 2 or 3 second segments instead though the stacked images will be a bit lower quality. As long as you keep a copy of your original video you can try multilple splits to see what's best.

All the programs mentioned are free and there are plenty of Youtube videos and web pages showing how to use them.

Taking single frames you have to wait to download each full frame in 16 bit which is limiting the number of images you can take in the 63 seconds. With video you usually record in 8 bit in high speed download mode and as long as you have at least 50 frames in each video segment, when stacked, it will have around 11 bit image resolution, which will be fine.

There's no need to have the mount connected to the image capture program as you can slew it to the Sun using Synscan If you have it or the phone app. If the mount is reasonably polar aligned it should track the Sun fine if solar tracking is selected, before, during and after the total elcipse. If it's going out of frame you can nudge it back in with the app or Synscan. The stacking programs will take care of aligning each frame so the Sun frames are well registered even if there is movement between frames.

You can practice taking videos during the day, or using the Moon to get more realistic practice.

I'm not sure why you had trouble connecting the mount to SGP though, If you have the Ascom driver installed for the Star adventurer. But as mentioned, for solar there's no need.

Alan

Most interesting Göran and another great image. It seems to show when in the vicinity of the reflection nebulae implying that it is composed more of blue reflection rather than OIII emission but it could be both.

My RASA 11 with the 6200MM and fast Astronomik NB filters is all ready to go now, but the weather here has been poor for the past week or so and no sign of any improvement for the next week either. If it does clear I can try it in OIII and see what shows up. 🙂

Alan

If it has edge notches or holes these are very useful.

Alan

Fixed. 😁 

Tried the 60mm black card mask on M51 again and the coloured diffraction effects and brightening around the edges have gone though the vignetting is quite bad. I used the same flat calibration frame from yesterday. Then tried it without a card mask but just put the Celestron filter holder back in place but without the filter glass present. The holder itself reduces the aperture from 74mm to 68mm and this cured the problems also, but with no real effect on the vignetting.

Here are grabs of the APP stretched stack previews of 12 frames per stack. The Moon was out, but near setting. 

60mm card mask in filter holder

68 mm mask by using empty filter holder.

So the moral of the story is, if using the Baader AFC system with a RASA 11, remove the internal filter glass but leave the filter holder in place. 🙂

Hopefully, after 6 RASA scopes this is the end of my RASA woes. Although one was my fault when I dropped it. 😖 Imaging here I come. 😁

Alan

46 minutes ago, pipnina said:

To be totally clear: You have a dew shield of some sort extending from the scope?
I could see light from the moon, street lamps, house windows or even far off-axis stars/planets refracting or scattering on the front corrector plate if it's not shielded.

Other than that, I don't know what to suggest as I've no experience with this scope, but I wish you a quick resolution!

Thanks @pipnina. Yes I should have mentioned there is a dew shield in place lined with Protostar flocking. Everything is the same as on my previous RASA 11, which didn't show this behaviour, except for now using the UFC filter system. It could still be a problem with the rest of the scope itself but I would then expect the whole image to show this and not just the edges.

I've now fitted a mask in the place of the clear filter which is removed from the scope if external filters are used. It fits very neatly and now recuces the lens exit aperture from 72mm aperture to 60mm. Should be clear later tonight to see if that cures it. Fingers crossed. 🙂

Alan

Long story short I have a new RASA 11 since last week and unlike the others, the collimation is correct and also no tilt issues, with very good stars over the whole frame so could start imaging right away. 😊 I've also fitted the Baader UFC system on this one mainly to avoid the severe vignetting on full frame. The UFC system is 70mm aperture from the scope unlike the Celestron scope adapter which is 48mm.

I started with the ASI2600MC and sure enough, no vignetting. Single subs all looked very good. However after stacking, the highly stretched previews in APP shows noticeable diffraction effects around the edges which vary a lot between targets.

The first was the Horsehead and I assumed the diffraction was a bright star out of frame so wasn't too concerned. However M51 and M101 show quite dramatic effects. M51 was imaged across the Meridian so the flip likely causes the repeated effect in the two corners.

I'm wondering if the UFC wide aperture is allowing reflections from the edge of the lens assembly in the corrector plate through to the sensor. I can try a black card aperture mask after the lens assembly tonight to see if that helps. Maybe the Celestron adapter masks to 48mm at this point for a reason. 🤔

Does anybody have any other suggestions as to the cause?

On normally stretched images the effect is not so obvious, but it upsets the background neutralization.  The Horsehead had the Moon quite close, while M101 had no Moon so the Moon isn't a factor. There are less obvious numerous curved diffraction effects on the right of M101 too, which may contribute to it being brighter there

Here are screen grabs of the APP initial previews. All used the same calibration frames.

Alan

1 hour ago, ONIKKINEN said:

Look up ASTAP platesolving, its what you are after. The H18 database is like a gigabyte, not a terabyte and i dont recall platesolving ever taking more than a couple of seconds (ignoring a few user error type situations...).

If your FOV is more than 1 degree then the H17 database should be fine, and that's only 500MB in size. 🙂

Alan

Very impressive Olly.

The lenticulars show possibly brown dust filaments in their outer edges, which Hubble images don't indicate, but on closer inspection the Hubble images just show the cores of the galaxies and the outer areas are not in the frame, so the brown bits are likely real and not artifacts. 🙂

Alan

That's a stunning image. 🙂

The group of stars and swirls just right of centre look as if they're an interacting group,  but it doesn't seem to be designated as anything.

Alan

6 hours ago, gorann said:

Thanks a lot Alan!

Interesting observation about possible shock waves from Tejat. I now tried to look for these in other images of the area. Almost all have a very blown out Tejat and with disturbing halos (apparently my RASA+ASI2600MC+NBZ filter made a good job at suppressing such artifacts), However, I found this image by Chris Heapy on Astroboin. I think is may even indicate that Tejat may be sending ripples through IC444:

https://www.astrobin.com/281272/

 

Yes there are circular like sections that are centred on Tejat which exend quite far. They could be interpreted as halos or flares but the edges look too undefined to be such.

It's interesting that the Chris Heapy image, which is also impressive, doesn't really show the closest shock wave as shown on your image, and Tejat appears more like a mini globular cluster too with the noise processing. 🙂

Alan

Another winner Göran. And yes, definitely two dogs. 😀 Plenty of detail in the fainter adult dog too.  It's eye, 12 Gem,  is actually a double star but StarXT has turned them into 2 well spaced stars.

Tejat looks to be surrounded by 2 shock waves, which is the identity disc on the dogs black collar. 😁

Alan

Another very impressive image Göran. 🤗 I like the framing, and contrast between the red and blue.

I think the Lynds catalogues need to be updated though, as they are rather arbitrary. LDN1382 points to a rather bright region and several other LDNs seem to point to nothing in particular. LBN681 points to a dark area by VdB14. Maybe it's meant to be the bright area to its left, while the bright area between VdB14 and 15 has no designation. 🤔

Alan

That's a great image, and one I don't think I've seen before. Very colourful. I'd call it the 'Fruit Bat Nebula' as it's looks to be eyeing up the raspberries. 😊

Alan

These Van Damme flexible cat5e cables, available in many lengths may be suitable though they aren't cheap. They are used in music stage productions so likely do lay flat on the ground. I've used Van Damme cables before though not network cables and they are high quality.

They are specified as unshielded though have STP stamped on the cable which means each pair is individually shielded. The unshielded refers to the RJ45 plug on the end which doesn't connect the cable shields to ground. Not a problem in your case.

Alan

Edit: The description does say it's UTP cable which is unshielded, so the picture likely isn't the actual cable used. UTP should be more flexible than STP anyway.

If you continue the brightest line of the white smudge off to the right, you end up intersecting the Moon. 🙂

Alan

A very useful tool to remove the blue halos if you have Photoshop is its camera_raw_filter which can be used on any image and not just camera .raw images.

Here's your first posted image with just one click of the Optics defringe module 'Sample fringe' eyedropper on one of the star blue halos. It doesn't just neutralize the colour making it grey but attempts to determine the residual colours below the halo and bring them forward. No image masking is normally required as only colours in the selected hue/saturation range are affected.

This is the latest Photoshop CC version. Earlier PS versions don't have all the latest camera raw features, so this may not be fully available as shown.

Here's your first image defringed. 🙂

Alan

If you plot the dark current figures given in the manual on a linear graph rather than the exponential one supplied you can see the actual effect of cooling it below zero is minimal when  compared to the other forms of noise present in the image.

I use it on my RASA and noticed that when doing a collimation test the heat rising from the peltier cooling causes a significant shimmer on the doughnuts above the camera which is much worse if cooled more, so I thought the increase in 'seeing' distortion when below 0C has a far bigger effect than the slight increase in dark current at 0C. 🙂

Alan

Just now, Ouroboros said:

@symmetal That’s a good point. Is moisture forming on the front cover plate of @Horwig’s camera or the sensor? 

If it was the camera front cover plate it would be significantly out of focus.

Alan

My ASI6200 does the same when cooled below 0C. It is condensation forming on the sensor. The anti-dew heater just heats the protect glass on the front of the camera to prevent dew forming on the front surface, but has no effect on the sensor dewing up.

It is there on the lights too but is very difficult to see on a single exposure.

Like my ASI071 it is not fully airtight inside so the internal dew tablets get saturated over time. Changing them is only a temporary fix as it'll happen again fairly quickly depending on how airtight it isn't.

When not in use, storing the camera in an airtight food container with a big pack of desiccant will help. Removing the accces port screw under the round black sticker when placed with the desiccant will help dry out the internal tablets quicker.

My ASI2600 doesn't have this problem and has never dewed up even when outside for weeks on end.

Zwo will reseal the internals under guarantee if returned to them I believe.

I also only cool it to 0C now to save the problem reoccuring. The improvement in dark current from 0C to -10 is very small and not worth worrying about in reality.

Alan

I have older Rhino cat 5 cables which are flexible but it seems their latest cables advertised as cat 5 are exactly the same construction as their cat6 with extra cable sheaths compared to standard cat5 making them stiffer.

It may be worth trying the flat cat6 cable like this which bends easily. It's possibly not as robust but may be better for your requirements. It seems to be usually available in longer lengths though, 5m or more though you may find shorter ones.

Alan

Edit: These are available in shorter lengths but you need to buy a pack of 12 in pretty colours. 🙂

Angular resolution is proportional to wavelength / aperture so imaging in near IR has around half the resolution of imaging in blue light, though as you say the effects of seeing is less, the longer the wavelength, so in normal seeing conditions the loss in resolution may not be too apparent.

It's likely the longer exposures are causing the softness as you're probably using 18mS at 55 fps. It's worth using very high gain settings to try and get the exposure to 5mS or less. It will look terribly noisy on the video but stacking several thousand frames will very effectively remove the noise. Also lower read noise at higher gain. There is no target rotation limit on video length with the Moon, so you can take 10 min or more videos and stack just the best 5 or 10%.

I assume you're recording in 8 bit and have the high speed setting enabled in the camera setup, (if it has that option). This reduces the A/D conversion depth to perhaps 9 or ten bits which will give a better fps, if you're not limited by exposure length.

Alan

Amazing Image. I like how M45 illuminates the dust giving it two arms you don't see in the usual Pleiades images. 🤗

Alan

The darks are purely related to the camera. As you have the cap on, the scope can't have any effect on the darks. Darks are often taken with the camera sitting on its own indoors, in the fridge. 🙂So use the same darks with any scope. As you say just the temperature, (and exposure) needs to match.

Your previous darks will be fine if they were at the same temperature and exposure. Usually it's common practice to take new darks every six months or a year just to take into account slight changes in the camera performance over time.

Flats are the only calibration frames which are specific to each scope setup.

Edit: You can use darks with exposures which don't match your subs if you enable dark scaling in your stacking program and have a master bias available, but as new darks are only taken very occasionally, you may as well have a set of darks which match the exposures you use for your subs. They should always be better than scaled darks.

Alan