david_taurus83

13 hours ago, Vic L S said:

Thank you. This is good to know. 

Do you know if the Celestron OAG will take the ASI462MC as a guide camera, as I am already using this as a guide camera on my current guidescope, trying to see where I can save some money! 

As long as you have the 1.25" nose piece for it I should think so. I will try and measure mine later and work out where the sensor is at focus.

On 27/04/2024 at 15:59, Vic L S said:

Thanks. I did come across some people saying the Celestron OAG taking quite abit of backfocus? But it's got a bigger prism. 

I might have to look at the OAG-L. Seems like a good compromise of prism size and having more backfocus allowance. 

The Celestron OAG does take up a good bit of backspace but if using the dedicated 0.7 reducer on the C8 you get 105mm to play with. I've had a few OAG units and this one is one of the best made I've come across. You can rotate the OAG prism independently of the OTA and imaging gear. The same with the imaging gear. It uses a dovetail like clamping system similar to what you get with Baader items. What I don't like about it is the camera helical focuser only uses 2 thumbscrews to hold the camera, not even a brass compression ring so you are likely to mark the barrel of the camera. Also, the prism only lowers down so far so with the C8 Edge 0.7 reducer, it is just about in the light path. It's OK if you have a big sensor like the 174MM but might be an issue with smaller sensors.

An excellent build! Are you in the construction trade Michael?

57 minutes ago, geeklee said:

That close up, FOV is crazy David, awesome   Is that still with the reducer?  Hope you get something before summer arrives.

Seeing it on the AZEQ6 has me reconsidering looking at one of these - it's (unsurprisingly) still a bit of a beast all in!  

Yes with reducer it's platesolving at 1480mm. I think native scale is around 0.5" with the ASI533MM or 1" binned 2x2. Guiding hovers around 0.6"/0.8". Hope we get better weather during summer as I will be imaging for the few darkish hours we get! My north view is pretty good apart from sky glow from Birmingham city so can keep popping at Cassiopeia and Cygnus in narrowband

1 hour ago, dweller25 said:

That doughnut image does not really confirm good collimation as it is too far from focus.

Ideally you should perform final collimation at perfect focus, on a high star and at x300 plus power - you should be able to see a perfect airy disk if seeing allows…..

 

Yes, your right. That would be the correct method for perfect collimation, in an ideal situation high up in the Andes with plenty and more time to fiddle with Bobs Knobs!

Back here in Gulf Stream Alley, the donut method is as good as I'm ever likely to get it. I doubt I will ever look through the scope until the planets come back around again. A couple of test images from the other evening. Single Ha sub of 5 mins and Lum sub at 60s. The Lum has a bit of guiding error it seems but stars are reasonably round. The Ha looks pretty good to my eye.

On 24/04/2024 at 12:35, Elp said:

When I'm using my C6 F6.3 reduced the dovetail position is very similar to yours. I bought a vixen saddle clamp that has threaded holes in the underside, clamp that under the dovetail near the front and screw in stackable gimbal weights (they're 300g each) under the vixen saddle. Near enough good Dec balance.

I got an ADM saddle for the mount. Can slide the OTA a bit further up now so all balanced without adding extra weight. Managed to collimate it with a tri bahtinov mask as well the other evening. Close enough I think! 

I got one today in the post. A nice 3D printed tri bahtinov mask from Ebay seller astrobyorlando. Some testing on my C8 Edge tonight. I've never owned an SCT before now but I got damn as near perfect collimation within a few minutes with this mask. I wasn't far out to begin with but it looks like it does the trick? It may be different with a newt as there are different angles involved?

On 21/04/2024 at 19:20, Fegato said:

I have an 8 Edge HD, but only use it with an OSC (ASI294MC Pro), and not at all recently as my RASA 11 tends to take preference. I'm not sure I can help much really, but thought I'd give you one response at least!

What I will say is that I'm surprised to see that much vignetting with a smallish sensor. What's your image train and what size filters?  I don't get anything like that with the 294 and 2" filters. And I'm afraid I don't know why you'd get such a bright central area with Lum. What method are you using for the flats?

As for collimation, I have the original screws not Bob's knobs. I find it holds reasonably well, and don't often bother to reset. But I think this is partly because I find the whole process a bit of a struggle - seeing always seems to be appalling when I attempt to work on collimation! Anyway - I wonder if your star shapes might relate to backspacing, as there's a bit of pointing into the middle going on? Maybe try pushing the sensor away a little and see if that helps?

 

Hi, the star shapes are probably a combination of poor collimation and imbalance in the mount. It is roughly balanced but just about on the OEM saddle. I know there are weight kits that you can use for the front of the dovetail but I really don't want to add weight. I have ordered an ADM saddle for the mount so should be able to slide the OTA a little further forward. Here's how it is currently.

On 21/04/2024 at 19:36, Elp said:

I think that's a very good result.

With my C6 I use the 6/8 inch flexible Celestron dew shield, it's not ideal because if you don't ensure its fully seated against the start of the dovetail it can shift slightly if you point it up and put a flat panel resting on top (haven't had an issue with it yet). A better solution would be the aluminium dew shield but it costs, there's also the storage issue (I pack mine away, the flex dew shield can simple wrap around the OTA and pack with it).

Regarding the flat, maybe you need to diffuse your light source even more. I used to have all sorts of issues until I diffused my panel with 4 pieces of acrylic starting from opal to almost black in colour, and put the panel on its dimmest setting. This ensures the auto exposed flats are a few seconds in duration (haven't done it at F6.3 for a while).

My collimation hardly changes, I would have thought it would considering the handling of the scope setting up and putting away (I'm also constantly removing the secondary for F2 imaging), the collimation is not as flimsy as a Newtonian which I was surprised by.

I got the scope with the Astrozap heated dew shield. I have to say it's a very nice piece of kit and the cut outs fit perfectly over the dovetail bar and the shield itself stays fairly rigid once it's on. It has no problem holding up my flats panel. You may have a point about the flats. I'm so used to refractor imaging and flats are just easy and always work. Mirror systems always give me flat foibles. I may try your suggestion and dim the flats panel for 5s exposures and take some flat darks, see if that helps. I have only used a master bias for calibrating the above.

Also have a 3D printed tri bahtinov mask coming from Ebay to see how it works with collimation. Will stick with the bobs knobs for now at least.

We had a few clear hours here in the midlands last Wednesday night I think it was. Just so happened the reducer and OAG turned up the same day so I was able to get some testing in. This is my first SCT so forgive the wonky stars as collimation isnt the best. I have orderd a tri bahtinov mask from ebay to try and help with this. I managed to get an hour of Lum data on M106 and 30 mins each in RGB. All 180s subs and binned 2x2 with the ASI533MM. Pretty pleased with the data considering the short integration. Its far from what I would normally post up but it was mainly a test image.

My first question is on collimation. How often do these need checking? It has Bobs Knobs at the moment but I may change. They are relatively tight so as they wont come loose but can they be too tight?

My second question is on flats. See below, the Lum flat has bright ring around the central bright spot. This has overcorrected the master Lum image. The flats were approx 2 seconds each and they were taken with the dew sheild on, same as the lights. They were not taken until last night so it could be slight shift of the mirrors but the dust donuts have been corrected so I'm not sure the time difference is an issue. Is there a particular way flats are taken on an SCT?

Are these the same as an SCT where you only adjust the secondary? 

Yes. The latest CMOS chips don't suffer amp glow anymore and their QE is typically higher and noise lower. They are also cheaper than CCD cameras. I swapped from an Atik 460 to an ASI 533MM and it is far easier to work with. Don't need such long exposures with it. That said, with any camera I have used, I still believe overall integration time needs to be over 5 or 6 hours for a somewhat decent image, regardless of whether it's CCD or CMOS. From a typical bortle 5/6 location anyway.

Edit: I should clarify, if you were looking to buy a camera now I believe CMOS would be the obvious choice. If you have a CCD and are happy with the longer exposures then there really isn't a need to change. They still produce great results with comparable integration times.

51 minutes ago, Simon Pepper said:

I have a 9.25 on the way and I am so excited. Will you use bobs knobs or do they hold colimation well? Thanks 

I have just got a C8 Edge. Haven't had the chance to set it up yet but it has Bob's Knobs fitted. They feel tight from previous owner and they prob do the job well enough but I will be changing mine to cap head bolts. I reckon you would get a better feeling of torque and more control from an allen key. Will be on a pier so hopefully should only need collimating the once.

I think it's a good idea. I don't know how many hours I have spent indoors/outdoors trying various tilt adapters trying to gey round stars in the corners. Would it not have been better to have 3 points of adjustment though? Must be difficult to get 4 to all contact relative to each other.

6 hours ago, Elp said:

I guess better to be over. But if that's the case why are all adaptors 12V? I usually use batteries and they run 11.5-11.8, never had a problem even in freezing cold temperatures. I have recently invested in some lifepo4 batteries for a modified rig, they however are gladly 12.8V.

The 12v adaptors are ok if you are using them as intended ie one for the camera, one for the mount etc If you try to use one to power everything, it will supply plenty of amps no problem but you may run into trouble with voltage drop. Thin cables between devices are the culprits.

16 hours ago, Elp said:

I assume you have a mains connection and ask if you need the 13.8V? May or may not be of use to you but the Pegasus mains adaptor is 12V 10A when normal adaptors are 5A.

I would always suggest using 13.8v as with smaller thinner cables feeding peripherals, there will always be voltage drop. Especially if there is need to run a long cable from source to mount. My Nevada unit is set to about 14v output and with the mount a few metres away and everything running the voltage at the mount is just above 12v.

On 25/03/2024 at 22:47, fireballxl5 said:

I've used a Nevada linear PSU to run a dual-scope imaging rig in my observatory for a number of years with no issues.  Looks like they've refreshed the design,  but equivalent I think to this one 

https://www.nevadaradio.co.uk/sharman-lm-30a-30-amp-analogue-display-linear-power-supply-unit-two-year-warranty?___store=nevada

 

I got one of these about 6/7 years ago and still going strong. It has been running 24/7 in the shed for the last couple of years now as it keeps power to the pier and dew straps to prevent condensation under the Telegizmo cover and also feeds 12v to the wife's barrel pond pump by the back door. Great investment. 

On 27/02/2024 at 22:51, AstroGS said:

@david_taurus83 I just started using NINA/PHD2  and the results are pretty consistent as well. For a reason I feel that it performs better now (round stars end-to-end) than previously although the figures say the opposite! Here are some recent screenshots from PHD2. Also, I am using shorter exp times (1 sec) vs the 2 secs that I had with the ASIAir Plus. However, I would say that on an average is around 0.7-1 consistently and ham getting round stars to edge even at 600sec exposures.

I did actually get round to doing a comparison of the AM5 guided by PHD2. As I suspected, the PHD results were more reasonable with an average guide rate of 0.8". The point of my thread was not to cast a shadow on the AM5 and its abilities, its a great mount and if I didn't have an AZEQ6 on my pier, I would have probably kept the AM5 as my main mount. I was trying to see if my long held suspicions about ASIAirs guiding graph figures were a bit on the generous side. Which they are!

https://stargazerslounge.com/topic/415062-asiair-am5-guiding-results/

On 28/02/2024 at 19:22, DaveS said:

My mojo.

Same. Not been feeling up for much astro lately. I used to check Clear Outside multiple time everyday seeing if there was a chance of a few hours. Relentless cloud for months and a rubbish start to the year has dampened my urge to do anything lately.

Have a look at your flats as well as it appears to have left a ring around the image.

If possible, I would be looking at returning the QHY unit and swapping for something that can go on the course side. In my experience, the Esprit fine focus design is not up to the task of imaging. It is essentially a Crayford design and will eventually start slipping.

I had a DSD AF3 which uses a belt around the focus knob. The AF3 itself worked flawlessly, it is the Esprit fine focus mechanism that wasn't up to the task.

The course knob does have a grub screw. You need to turn it to access it through no 1 hole I believe.

The Esprit focuser is rack and pinion but only on the course side. The fine focuser mechanism is a sort of Crayford type design. I had an auto focuser on this for a while but the fine focus started slipping. I had to change to an auto focuser to fit the course side. Not all auto focus units have the torque to move the course side though.

On 04/01/2024 at 19:12, ollypenrice said:

I'll say it again: dither is for DSLRs and, maybe, CCDs. 

CMOS?  Why?

Olly

And CMOS. I don't bother with the task of taking multiple sets of darks for different exposure lengths. Just a set of Bias frames for a master bias and dithering takes care of hot pixels and walking noise. That is of course with the newer CMOS with no amp glow.

This was hard fought material to gather. Started back in October and gathered the last sessions worth a few weeks ago. Almost every night was mithered by unexpected clouds and the best nights weren't forecast clear at all! Still, managed a touch over 14 hours worth. It's a bit brighter than I would normally process but all that dust!

Esprit 100 and ASI2600MC, no filter.

421 x 120s subs, 100 gain, 50 offset.

Processed in Pixinsight.

Looking forward to seeing this on the market. In true Skywatcher style, it will no doubt be offered as a package on an EQ5!