alexbb

Latest additions to Veil for a total of 4h Ha and 6h O3. M27 RGB: 23 minutes each channel. M27 RGB-HOO: RGB above + 1h Ha + 2h O3. 2 versions. I guess this would be all for at least a week. Thanks for watching, clear skies! Alex

Nice! I need to get some colour too, but I only have a window of about an hour before it gets out of my sight. And then I switch to Veil. I might try to put the DSLR too with the Canon lens and try to get some coloured stars.

What do you mean by throwing money at your 80ed? What are you upgrading on it? The 130 reflector will provide a much larger light gathering area therefore increased resolution, but having a central obstruction will also put some more light on the outer airy layers so the stars will look a little more bloated. You should get good stars with the 80ed, especially in nb. It's the light gathering time that is much longer on the slower frac in order to get the same amount of photons from the same area of sky. I was pretty close in buying an 80ed, several times, but in the end I bought a sh Canon 300 F4 L lens and I'll save for a new Esprit. But 75% of the nights I'm limited by seeing to ~2". And, btw, my 130PDS was also bought sh, only the coma corrector being new. Thanks! I'm hoping for at least twice the amount of integration time, but I'm pretty disappointed by the resolution. For the O3 nights I had the PHD reporting me ~2" RMS total error, for the Ha I was luckier to have a better seeing of 1.6" or so, which is still worse than the resolution of the 585mm FL and the ASI1600 sensor are aiming for. For the M27 I didn't even bother and I binned 2x2. I would try it if I were you. Just remember how much you turned the screws so you can revert if it's worse.

Also, I have now one more O3 hour on the Veil for a total of 4.5 hours of O3 and 2.5 hours of Ha. I also acquired one hour of O3 on the Dumbbell 30 mins of 60s exposures and 30 mins of 180s exposures stacked in DSS with HDR stacking mode. Overstretched and very noisy. Though, it's an improvement over my last year's attempt at M27, I can't remember how much data I had, but there were just a few subs taken with the DSLR, but under better skies. Thanks for looking, Alex

I always assumed that this is their purpose, but I didn't mess with them as I didn't need. Aren't they allen screws? I'm at work now (lunch break) and I'm not near the scope to confirm. Being allen screws, I remember that I could access them maybe with the short side of the allen key.

Same as Adam, I pushed the primary up the tube, but I also changed the screws with longer ones. The focuser still pops in the light path, but just a little.

Glad you sorted it out. And yes, it should apply to reflectors too. On another note, my focus routine for the last 3-4 sessions was just to place the bahtinov mask and check the focus. But, on the other hand, the ASI 1600 + the manual filter wheel are lighter than other camera combos. And one more iteration of the Veil, this one with almost 3.5 hours of O3. I shot last night one more hour of O3, but it's not processed yet. The seeing was not very good when I shot the O3 so the image is resized to half and even the small stars look pretty big. I won't put much effort though in processing until I have all the data I want. I plan to gather at least 5-6 hours on both Ha and O3 before I switch to something else, but it seems that the weather does not allow this soon. Clear skies and thanks for looking, Alex

I think this can explain what happens:

I finally decided to properly try to use the 130 for imaging, even if I have the CC for many months now. The M13 is from 14th May made from ~40 of 120 5s unguided exposures and ~20 minutes of 30s guided exposures. The seeing was not very good, but choosing the best short frames helped. Luminance only, 139 gain, cooled to -15C. The Eastern Veil is taken during 3 nights, 2 of Ha for a total of 2.5h and 1 of O3 for a total of 2h, all in 180s guided exposures, 300gain. This one was reduced to only half the resolution, the seeing during the last night when I shot the O3 being worse, maybe around 2"/pixel. I still don't understand why it's so blurred, I was expecting a much sharper result out of 4.5h. I have to acquire more data when possible. The main issue for me and this scope is with the flats. I took them with an unfolded white T-shirt at dusk, but they seem to overcompensate. I have to figure out why or at least how to counteract that. Maybe during this weekend. Anyways, here they are. I might start to like this scope in the end. Clear skies, Alex

I made some tests with various distances and, indeed, the results seem better with a shorter distance. I rechecked the collimation too and I tried to get it as close as possible, using the APT collimation aid tool this time. I couldn't take proper flats so I'll post the results later after I'll take them. There's also a possibility for some clear skies tonight.

Hi, Michael I'm expecting to have coma to some extent, but there's not only coma in my pics. If I had only coma, I'd expect the stars to look like in my uncorrected newton. Stretched quickie with my 130 from last year is attached. It seems that I might see some stars tonight through high clouds, could be fine for figuring out the spacing. Fingers crossed, I'll keep you informed. Alex

Yes, I tweaked it a little since then. At center the out of focus star had concentric disks/circles in and out, as much as I could tell visually. I didn't use any collimation aids, just that the disks/circles looked concentric from just a little defocused to very defocused.

I understood the same too by reading reviews, discussions, debates, etc. The vignetting should be less for the 4/3" sensor and it's possible to correct it with flats. I don't plan to use it with the DSLR. I also understood that the closer you place the sensor to the reducer, the better the field is flattened for this design. This is how my stars look without the f/r and with a DSLR I was also aware of the info in the link you provided, but, as I mentioned before, I read that getting the sensor closer yields a flatter field. And it also seems that the stars in the Crescent frame look better than the ones in the M13 frame. The Crescent was shot with a shorter distance. I have a 7.5mm extender so I could replace the VariLock adapter or the other one with the 7.5mm extender to shorten the distance or I could add it to the VariLock and increase the distance. But I don't have clear skies anymore. I took this information as correct: https://www.cloudynights.com/topic/305891-back-focus-question-for-c6-sgt/ Thanks, Dave! Alex

Hello all, I bought relatively recent a SCT 0.63 reducer/flattener for my C6. I'm planning to use it with the ASI1600 camera, but it seems that I can't figure out the proper spacing distance between the reducer and the sensor. That or there's another problem with the scope that I can't figure out. The first distance that I tried was ~105mm. I achieved this by using a SCT adapter to T2 which is 50mm + a Baader VariLock set to ~28mm + the filterwheel 20mm + 6.5mm the distance from the sensor to the camera thread. + the filter width, it should be ~105mm. I understood that the closer the sensor is placed to the flattener, the better the field is flattened, but the reduction is weaker. I didn't mind that. I then tried to use an M48 (has also a T2 thread inside and deeper) to T2 adapter which was about 15-20mm. In both cases the stars were not in focus away from the center, with an out of focus elongation towards the edges (I don't know which word describes this). The following M13 is with the Baader VariLock and the Crescent was with the shorter adapter. I didn't have time to test without adapter at all and now it's going to stay cloudy for a while. Don't mind the quality, the M13 is unguided with ~20min (6s subs), the Crescent is ~20min (1min subs), guided. Very bad seeing. Did anyone use a C6 with a 0.63 reducer/flattener and APS-C or 4/3 sensor with success? Or does somebody know which is the correct backfocus distance and how to get rid of the distorted stars towards the edges, but still using the same scope + flattener? Many thanks and clear skies, Alex

Congrats and clear skies! Just keep the EQ5 too for the moments you'll need both visual and imaging

No, I think that the clutch in that video is not tightened enough or the mount is defect. That's how mine would behave if the clutch was not tightened. Yes, it's possible, though I wonder how you can fine adjust the azimuth when you want to polar align. In AZ mode it's not needed, but make sure that you tighten the mount on the tripod well enough so that it doesn't behave like in the video above, but because the mount itself rotates above the tripod.

Going to sleep so I'll reply short about the az-eq5: I didn't encounter issues because of the pier and short legs, I have also an eq5 with a classic steel tripod. Also I never felt the need for a polar scope after I learned how to use the polar alignment procedure from the handset. And about the finder position, you can put the scope on the other side, but you should try to balance it if it's heavy. Preferably with another scope HTH, Alex

It might also happen that you have a good PA and small periodic error and you guide on a hot pixel. How level is your guiding graph? Small chance though.

Let's lower the mean: 2 taken with the ASI 1600 MMC and a Tair 3s lens, Ha only; 1min subs, guided. IC434 and NGC2237. 2 taken with both Canon 450D and 550D, both on their Tair 3s lens. 5min subs, guided. M31 and M45. 1 taken with both Canon 450D and 550D, on their Tair 3s lens, 30s subs, unguided (laptop battery went out) + some Ha addition taken with the ASI 120 MM with a 135 CZ lens and one Tair 3s. M42. Alex

Imagine you are doing the flip manually and imagine that the situation shown in the drawing describes a scope with a magnification of 1, but the scope is tilted away from the dovetail clamp (as described before by @Stub Mandrel). First you rotate around the RA axis 180 deg. Then you rotate around the Dec axis as shown. The coloured stars are then away from the center. What you need to do in the case described to center to the same FOV is to rotate the scope around the RA axis counterclockwise and around the Dec axis ... can't compute at this hour how you have to alter - add or subtract to the degrees number, but there's an arrow for that. Does this make sense to anyone? Maybe I can explain better when I'm awake.

If you have the offset and then you try to center to the same FOV, you need to rotate the axes. Hence the rotation. You should be able to experiment this by pointing to horizon during the day and center on the same point, on both sides of the mount.

It depends also on the cone error type. If the dovetail is shifted sideways to the scope, a Dec axis slew will point to the same place. If the front (or back) of the scope is farther away to the dovetail, then you have to slew the RA axis too to recenter. This will also happen if there's something caught between the dovetail and the mount clamp. I'm trying now to figure in my head how much this matters if you're imaging closer to the pole.

How do you realign after meridian flip? Plate solving or just leave it as it is? Because if you try to recenter on the same point and you have a cone error, you have to rotate the axes to point exactly in the same place as before. Btw, how does the mount compensate for cone error if you do a 3 star alignment? I never needed to do a meridian flip for my balcony imaging and neither when going outside wasn't mandatory as my mount traks past meridian. Maybe you don't even need to recenter after flip, the mount already compensates and that implies some rotation.

The outer area was taken through an 135mm lens in a relatively short session compared to the others. The smoother area has more data taken with a 300mm lens and then all manually aligned and combined. You can also see how the stars are much tighter because of the larger lens and longer FL. And Alnitak's companion as well.

I'll post 2 of my new images taken in AZ mode since I can't set up the mount on EQ mode to point in this area without the balcony window's frame getting in the way. So.. AZ. I recently acquired a Ha filter and put it on an ASI120MM. New camera acquisition is planned. You can find more details about the images and their evolution here: Clear skies, Alex