alexbb

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

Some more data taken with the Pentacon 200 F/4 and the Tair 3s 300 F/4.5. All data combined so some areas are less noisy, on the outside usually they're more. I could crop, but I'll let you see the differences.

More time on Rosette:

Reprocessed the Orion and the Horsehead. Added then the Ha layers as luminance on some colour images and also the Ha to the red channel: Edit: colour images detail: M42: (~50x30s@ISO1600 + ~10x6s@ISO1600)x2 - Dual setup with Canon 550D and 450D both on Tair 3s F/5.6 IC434: (45-50x30s@ISO1600)x2 - same setup as above

Clear this night until an hour ago, then some clouds rolled in for a while, but tomorrow morning back to work so I should go to bed. M42: ~100x20s + ~50x5s + 100x2s + the one above slightly blended for the core IC434: ~100x20s NGC2244: ~45x20s All at 70/100 gain. Definitely better than I expected, but maybe next time I'll think at framing too. Clear skies, Alex

Bin it and you have a chance

Hi all, I wanted to buy my first narrowband filter. I decided on a 7nm Ha filter. Among the options, there were the Baader 7nm and the Optolong 7nm. I chose the Optolong even though I heard that the colour ones are Astronomik copies. However, I searched some comparisons between the Baader and the Optolong and the Baader seemed to have some halos. I decided on the Optolong. However, I don't have a proper imaging camera and for a while I'll be testing it with the ASI120MM I have. Plans for a larger sensor camera. Yesterday I received the filter and had some tries on M42. My balcony window opens to NEE so M42 is a tough target. I can only point the scope to it on EQ mode only before it reaches 15deg. So I had to switch to AZ mode where a scope can reach almost out of the balcony with the counterweight bar extended. Very good AP setup. Anyway, I attached the ASI120MM to a Tair3s lens, wide open this time at F/4.5 and put them on the AZ-EQ5 in AZ mode. ~40x10s + 70x2s. Gain 70/100. With calibration files. I don't know what to try this evening if it's clear. What do you think about putting the camera on a 135 F/2.8 lens and drizzling 2x? Did anyone of you try drizzling and had a successful result? Clear skies, Alex Edit: I don't know what I've done to have the white frame, I didn't notice it until now. It was probably after combining the 10s image with the 2s one.

Thank you, Nige! I think it was because the scope wasn't new.

On another note, on topic: I just bought yesterday a sh Celestron C6 from a local club colleague and I set it up along with the ST102 in the beginning, and then along with the 130P-DS. Side by side on the AZ-EQ5. In the beginning, they were mounted only for visual and the sky was cloudy, not even the moon was very visible. After a while the clouds wend away and the moon was lighting all the sky, but then it got pretty foggy. I saw some bright clusters, the scope kept its collimation during the bagpack transportation, perfect concentric circles. After about 2-3 o'clock, the sky cleared, only the moon keeping it bright. After observing with both scopes for a while, I decided to put the camera on the scope to show to my girlfriend what we could barely see before she went to bed, the sky being still foggy. M35, M36, M37, M38, all 20x10s lights, 20 darks, 20 flats, didn't care about bias. ISO3200 with the Canon 550D. And the moon at about 6 degrees over the horizon.