johnturley

Last night was the first clear night for me for a week, and not likely to get many, if any, during the coming week so took the opportunity to image Mars.

Conditions were not ideal with quite a bit of unsteadiness, a heavy dew coming down, and the best view was through the Esprit 150. The image below was from a 3-minute exposure with my ZWO ASI 462 Planetary camera using a 2.5 x Powermate, 28,000 frames, average frame rate 156 fps, capture area 296 x 296, processed in AutoStakkert and Registax.

Last Night was misty, but some of the most stable atmospheric conditions I have experienced recently, in fact one of the rare occasions the 14in Newtonian gave a better view of Mars than the Esprit 150. North Polar Hood stood out quite nicely and was easy to see visually.

Image taken using a ZWO ASI 462  Planetary Camera, Baader UV/IR Cut filter, 2.5x Powermate giving f12.5, 2 minute exposure, 13,000 frames @111 fps, processed in AutosSakkert and Registax, plus a bit of final polishing in Lightroom.

16 minutes ago, Magnum said:

I found this comparison I did on Sept 4th with my old 224C, colours is slightly different between the 2 as it was only a quick comparison, and I really cant be bothered to process it again from scratch.

Anyway the left image is at prime focus with my 12" LX200 but with extra spacing the disc measured 250 pixels which works out to be F13, the right image is using my 2.5x Barlow measuring 480 pixels and is bang on f25. I have enlarged the f13 image to match the f25 image size. They were taken about 30 mins apart and conditions were pretty consistent throughout the session. To my eyes the f25 image is way more refined.

Ive since upgraded to the 462C with smaller 2.9um pixels compared to 3.75um on the 224C so ive dropped my working FL down from f25 to f21 now to get me similar scale.

the ideal sampling maybe somewhere between the 2, but I would conclude same thing Neil said, its better to oversample than to undersample

Lee

Do you find the ASI 462 with its smaller pixel size a definite improvement over the 224.

John 

5 hours ago, neil phillips said:

Some single runs. may try de rotation later 

Orion 245mm Newtonian QHY 462C no ADC. EQ5 PRO

Optimal sampling F14.175 Baarder Q 2.25x RGB

100%

resample

 

Oversampled F26.775 Baarder 2.25x + Celestron Ultima 2x 

100%

Personally think too much is made of sampling rate. As can be seen not much advantage correctly sampled. And seriously oversampled isnt really hurting the image that much. Long discussions over pretty much minimal effect, I think. As long as your not under sampled and not ridiculously oversampled. It doesn't really have a huge effect. Not one i am seeing anyway. 

 

 

Fantastic image Neil, Mare Erythreaum and North Polar Hood showing up really well.

I could see the North Polar Hood quite clearly visually at about 12.30 last night, I was just about to take a few images, but then it clouded over.

I regularly use a 2.5x Powermate with my Esprit 150 (f17.5), which gives reasonably good results, yet some observers suggest that I should be aiming for around f9 (1.25x Barlow) to optimise the sampling rate, and Astronomy Tools ridiculously suggests that under O.K. Seeing Conditions I should be aiming for around f5 (0.7 Reducer).

John 

2 hours ago, bomberbaz said:

I am rubbish at maths and as much as I try, it's all greek to me.

SO I use this calculator instead astronomy.tools

The results from Astronomy Tools comes up with might be meaningful for Deep Sky imaging, but they are a nonsense when it comes to Planetary Imaging.

Rather than using a Barlow with my Esprit 150, it suggests that under OK Seeing Conditions I should actually be using a Focal Reducer with my ZWO ASI 462 Planetary Camera (pixel size 2.9 um)

John

Excellent Kon, lots of detail in the Mare Erythraeum area, and the North Polar Hood showing really well. 

When you say resized 120%, what software did you use

John 

44 minutes ago, imakebeer said:

Can you elaborate on this @Freddie , why would you do this? What is it that's so bad about eyepieces, why are Barlows better?

From what I've read, the dogma is, yeah, use a Barlow. But...

I think I tried it a week or two ago - opportunities have been rather scarce lately, mind you!

Apart from being the right way up, I think the images were maybe slightly worse and certainly not significantly better. That could be down to seeing, or altitude of Jupiter at the time, or maybe my Barlow is rubbish...

The image in 5x live view mode was same size or similar...

I'm more than happy to try again when I get the chance, I'm just curious to understand why a Barlow should in theory be better?

Cheers! 👍

I agree, there seems to be a general taboo these days against eyepiece projection, although it was quite commonly used before the advent of dedicated planetary cameras with their small sized sensors compared to DSLR's. 

There was a post on 'Cloudy Nights' recently where someone posted some quite good images using eyepiece projection with a Baader Mark IV 8-245 mm zoom eyepiece set at 8mm, and a Takahashi 100 DZ telescope. 

In my opinion the image size using a 2x Barlow with your setup, would have been too small to be able to obtain a decent array of alignment points in Registax or Autostakkert.

John 

Nice capture, and North Polar Hood showing up very well.

John 

3 hours ago, NGC 1502 said:

Indeed I have that book along with several similar by Richard Berry, Reg Spry, Charles Frank….

Fully agreed an optical window would be an extreme solution, but it has been done!   Not an option with a basic workshop like mine but one for an optical expert with a relevant optical workshop and time to spare!

Astronomical Equipment, Luton (not Astro Systems), used to produce Dall-Kirkham Reflectors with optical windows in the 1970's (see attached images), would be interesting to know how many of these they produced, and how many are still in use.

They claimed that these instruments would perform similar to a refractor of the same aperture, maybe a bit optimistic, or maybe not if you compare them to the refractors that were available at the time.

John 

18 hours ago, Astro_Nic said:

Yeah but he’s not using a manual dob! 

I understand that using a manual dob makes planetary imaging more difficult, but several observers such as Kon (see his recent Mars posting taken using a manual dob), produce some excellent results using these sort of set ups.

John 

58 minutes ago, Astro_Nic said:

so 2.5x 1.25" powermate or the 2x 2" powermate?

 

5 x 2um = 10 um optimum?  Although someone has mentioned that with the ADC it might be 2.2x barlow effect so 4.6 x 2.2 =  10.16......   That's a 3,500ish FL for a manual dob.  Looks perfect sampling

 

The 1.25" powermate is interesting as it's sp much cheaper.  But this gives a 4,000 FL or more with ADC and a 2.5x (2.8x?) x 4.6 = 12.9....too over-sampled? and harder to use?

 

Over-complicating it?  Maybe I just don't need a powermate and just get a 2x televue barlow and forget it for visual?  Have 22mm (2 inch), 13mm, 9mm, 6mm, 4.5mm eyepieces

Help!

Thanks! 

Don't worry about possibly over-sampling with your proposed set up.

Geoff Lewis regularly uses f22 - f24 with his C14 and ASI 462, and gets good results.

John 

I generally use a 2.5x Powermate with my Esprit 150 (f7) and ZWO ASI 462 camera, which gives f17.5 and effective fl of 2650mm, I tried a 5x Powermate, but the results were not that great, although it might work ok on Mars under very good atmospheric conditions.  

With your f4.6 VX14 (fl 1600 mm), a 2.5x Powermate would give f11.5 (which incidentally is supposed to be close to the optimum for the ASI 462), and effective fl of 4,000 mm. I gather however that you were thinking of the ASI 678, which has a larger 1 /1.8 " format, so the image size would be similar to what I get with the Esprit 150 and ASI 462 with its smaller 1/2.8" format, so no a 2.5x Powermate would not be too powerful. 

John 

1 hour ago, Astro_Nic said:

Thanks.  Would 2" future proof me?  Just wondering if it will cause any issues in the image train.  Am getting a 2" powermate and have 2" focusers etc - no idea what thread is on the camera.

Thanks for your help.

 

Any brand worth getting or are they all about the same?  What's the difference between IR/UV and just an IR cut?

1.25 in filters should be fine for up to 4/3" sized sensors, but 2 in for larger sizes.

If you are imaging planets you don't need a 2" Powermate, not only do these cost more, but they also add significant extra weight to the system which can result in balance issues.

Most ZWO Cameras (up to 4/3 " format) have a T thread, and come with a T thread to 1.25 in nosepiece, which is threaded for 1.25" filters.

Most observers recommend using an IR/UV cut filter for imaging planets such as the Baader one below, although cheaper brands are available. 

Baader CMOS Optimised UV/IR Cut and L Filter | First Light Optics

Hope this helps. 

17 minutes ago, Astro_Nic said:

Thanks.  Excellent help.  I think I will stick with the 678.

 

In terms of filters, is there any benefit to a 2 inch one?  Or stick to 1.25"?  Money not an issue.

 

Thanks

 

Nic

With the sensor size of the ASI 678 you don't need 2in filters, 1.25" is fine.

If you were to use a camera with a full frame sensor you would need 2 in filters. 

John 

14 hours ago, happy-kat said:

Every night or even hour might be different seeing and atmospheric conditions, perhaps evaluate after several sessions. Why not try using prime focus.

 

 

If imakebeer used prime focus with his SkyWatcher 900mm/70mm refractor and Canon EOS 450D, the image scale would be tiny, eyepiece projection is usually required with digital SLR's to get a decent image size on planets.

John 

53 minutes ago, geoflewis said:

Thanks Vlaiv, I think you may have hit the nail on the head. It may just be that it is easier to dial the focus with a bigger 'oversampled' image on screen. I certainly found this to be true when Mars was last close to us in 2020. I was operating at ~F22 for Mars in 2020, but only F12 for Jupiter and Saturn last year, but of course Jupiter and Saturn were much lower down and imaging them at all was very challenging. So far this year I have imaged all three at F12, but I am going to experiment with different amplification to see what differences I get, especially with Mars smaller diameter this year, but up at ~60° elevation.

Thanks for all your advice on this complex (to me anyway) topic.

I agree with you Geoff, imaging at the supposed optical focal ratio often results in far too small am image, which makes it more difficult to focus on the laptop screen, and to set align points in Registax or AutoStakkert.

John 

41 minutes ago, paddyb said:

Ok, thanks. I'm obviously not understanding Moonset, which I would take to mean that the moon is below the horizon? So if it sets at 20.56 on the 26th, why would I see I crescent moon after that time?

I will hopefully have other staergazing opportunities in future years, but this year Morocco is the best I can do do. Will I still see some of the Milky Way?

No, you wouldn't see the moon after that time, it's just that the constellation Sagittarius in which the richest part of the Milky Way is situated, would also have set.

The best time of year to see the Milky Way from Moroccan latitudes would be late summer/early autumn, having said that the 3-day old crescent moon might not interfere too much with the view on the 26th November in particular. 

John 

6 minutes ago, paddyb said:

I’m going to Morocco later this month and hope to get out into the desert to gaze at the Miky Way, something I’ve always wanted to do.

 

Obviously I should be looking at being out there for there for new moon, which is on 23 Nov, but looking in more detail, it appears that the moon sets quite early in the evening during that week, so would it matter if I went a bit later that week, on the 26 / 27 for instance, when it sets at 20.56 / 22.07? If I went out after those times, would the be any light from the moon to interfere with the stars?

 

Probably completely misunderstanding this!

 

The richest part of the Milky Way lies in the constellation Sagittarius (which can't be well seen from U.K. latitudes), unfortunately the waxing crescent moon would be in the region of the sky on 26/27 November.

John 

28 minutes ago, StevieDvd said:

Y

Sharpcap will let you select the camera from the menu and tends to show an image with auto settings - so a little more user friendly for first use.

 

 

I agree, I find Sharpcap more user friendly than the ZWO ASI software.

Sharpcap is available for free download (currently on version 4.0), and there are quite a few good videos on YouTube regarding how to use it.

John 

On 02/11/2022 at 09:59, Magnum said:

im not so sure Geof, depending on the seeing im using my 12" LX200 at between f21 & f25 with the 462. on most nights I find f23 gives the best detail for me, so thats around 7000mm FL, on poorer nights I go down to f21 which is just over 6000mm FL. 

I have just bought a Baader Q turret 2.25x barlow ( only about £45 ) which seems as good quality as my GSO2.5 App barlow, but has the benefit that the end can be removed and screwed straight into an ADC giving a more modest  1.3x mag so that could be a nice option for you to get just a little more if you don't want to go as crazy on the mag as I am. 

I think it would get you to about f17 & 6000mm FL which is about the same FL as mine at f21.

Lee

 

That's interesting Lee that you get good results with the ASI 462 at f21-25, I usually use a 2.5 x Powermate which gives f17.5 when imaging planets through my Esprit 150 with my ASI 462, which gives reasonably good results.

However, some people suggested that I should be aiming for just 3x the pixel size of the ASI 462, which would be around f9, but with the focal length of the Esprit being just 1050 mm, f9 would result in too small an image size, and led me to believe that the ASI 462 was not the ideal camera to use with the Esprit 150, and that I would have got better results with the cheaper ASI 224, with its larger pixel size, tempting me to buy one of these.

John 

11 hours ago, impactcrater said:

 

I also was surprised to learn you can see Neptune so I will try for it when it is in the right spot for me.

I am near Sydney Australia.

Happy sky hunting!

Neptune is currently magnitude 7.8, so you require binoculars or a small telescope to see it.

It is situated in Aquarius so from Australia it will be high up in the northern sky mid evening, transiting at around 9 pm local time. 

John 

11 hours ago, Kon said:

Mars at 630am this morning. Mist and fog was not helping but fairly stable. I have played with the edge rind in Gimp and I think it looks tidy; no layers just an inverted selection, followed by brightness reduction and a mild gaussian blur. I am happy for feedback; is it good or is it looking not quite right etc?. Original size and resized 120%. 8" Dob, manual, asi462mc, 2.5x TV powermate.

 

original size

 

120%

 

image after registax

North Polar Hood showing very nicely

John 

The weather forecast for this morning's partial solar eclipse was not great, but unexpectedly the clouds cleared just after the eclipse began, so ended up with quite a good view, although there was intermittent cloud from time to time. 

Photo was taken through my Esprit 150 with a Canon 6D digital SLR, and using a Seymour Solar Filter.

John  

6 hours ago, Freddie said:

Why? I believe the Nikon pixels are 5 micron so with a 8SE a 2x Barlow would be about right for typical seeing.

Well try it, but I think you will find that the image size will be extremely small with the size of sensor you get with most digital SLR's, and I don't think that many (if any) allow you to crop the capture area so as to enlarge the image scale, I can't with my Canon 6D.

John 

If you want to take photographs of planets with a digital SLR you will need to use eyepiece projection, otherwise the image scale even if using a barlow lens will be far too small.

You can use either an eyepiece projection tube, or an adaptor available from Baader which fits their Hyperion and Morpheus range of eyepieces.

Attached is a photo of Mars I took in September 2020 using a Canon 6D digital SLR attached to my 14in Newtonian, and using eyepiece projection with a 9.7 mm Plossl eyepiece. Not too bad maybe, but nothing like as good as can be achieved with a dedicated planetary camera. 

John