Magnum

Just now, geoflewis said:

Thanks Lee, that’s the configuration I was thinking to use . I’m going to try the Baader lens on its own, screwed into the nosepiece of the camera (I’ve already confirmed that it fits ok). So the configuration will be scope -> ADC -> FW -> Barlow lens -> camera, but I’ll be experimenting as you suggest. I use FireCapture for capture, but can set the ROI in the same way you describe to measure the planet - I can’t believe that I never thought to do that previously 🙄. I’ll then reset the ROI with a bit to spare around Jupiter for the capture itself.

I just added a bit more to my last reply while you were typing yours

11 hours ago, geoflewis said:

Thanks Lee, yes, I'm aware that the change in magnification for TV PMs is different than how it works for barlows. As the below chart of the TV website, shows there is definitely a reduction with the x2.5 PM the further it is from the sensor, but for the x2 PM the change is very marginal.

It's one of the main reasons I moved from using the TV Barlows to the x2 PM. I have the ADC between the PM and camera as the ADC is 1.25" diameter, whereas the PM is 2" diameter. I'm also using a FW, so that increases the distance to sensor a bit too.

Oh that's a good chart, yes the 2x does seem to have a negligible change doesn't it.

OK, so I would go straight for trying the new Baader at 1.3x, but I would put the ADC and or  filter wheel in front of the Baader 1.3x . if you keep the ADC in the middle like you have it now the spacing will be too much for the Baader and make it act at something like 2.5x.

Though they do say that ADCs work better at higher FL, there is a point where the optical aberrations introduced by the ADC become more important than the gain from removing the dispersion, but as your scope is already f11 I would think its already above the point and shouldn't be an issue. 

You will need to have a play around with the order while previewing Jupiter to get the image size you want, a quick and rough way to check is to adjust your ROI box in the capture program if the planet just fits in the ROI then you know thats how big it is. You can set any custom sized ROI in sharpcap. I like Jupiter to be around 480 pixels at the moment now that its apparent size has shrunk a bit.

Remember all the maths is fine and important, but doesn't hurt to test it with experiment 🙂 and I like to experiment by finding the best images in the world then replicating what they are doing. Mr Peach has been the best planetary imager in the world for almost 20 years he's working at 0.08"-0.1" so I find it very hard to argue with that.

Saying that I think Marco Lorenzi has now surpassed Damian with his last few images since he upgraded to using a 21" dob on his balcony in Singapore, he's also working at 0.8"/pixel https://www.glitteringlights.com/Images/SolarSystem/Solarsystem/i-gJzz7J8/A

Lee

11 minutes ago, geoflewis said:

Thanks Lee. This whole discussion the last couple of days has been eye-opening for me. I've just fairly blindly followed the px_size x5 rule of thumb, then watched the on-screen image to see what worked. I felt including the x2 PM with an ADC was too much and I think last year I took the PM out when imaging Jupiter which was still very low down. On Anthony Wesley's (Bird's) advice I'd taken the ADC out for Mars in 2020, but I was happy with my results still including the x2 PM. As I discussed with @neil phillips yesterday, I think I was too hasty to give up on the x2 PM with the 462MC sensor, but with the Baader barlow I have some options to increase amplification without going as far as 0.07" / px. It will be good to experiment some more, as Mars moves towards opposition over the coming weeks.

Yes I think if you weren’t using an ADC then you could use the 2x powermate, but the adc will push it a bit too far so the Baader barlow will get you something in between. 
rember though that with barlows extending the spacing increases the magnification, but with power mates it’s the opposite, extending the spacing decreases the magnification. So you could theoretically back of the mag with your power mate by using a bit more spacing.

do you have the ADC before the barlow or between the barlow and the camera? As that makes a big difference too.

Lee

3 minutes ago, geoflewis said:

Phew....!! So I've checked my images with the ASI290MM from 2020 and see I was very similar to Go & Peach at 0.07"/px and according to FireCapture FL = 8500mm, equivalent to F23.

That worked really well, so I'm definitely going to try again with the ASI462 at greater amplification.

From UK 0.07” will be pushing it, but around 0.09 - 0.10” is doable

42 minutes ago, geoflewis said:

Thanks, I just did that and got 345 px, so very similar to the 349 that WinJupos gave me. I did the maths myself based on Jupiter's diameter at 49.2" on that night which confirms the ~0.14"/px (49.2/349). So am I actully then already oversampled without any further amplification....?🤷‍♂️

In Damian’s talks he classes anything below 0.06” pixel as oversampling, 0.08” - 0.10” as ideal sampling , and 0.14” as under-sampling. 
this is for scopes in the 30-40cm aperture range.

im attaching screen shots from his talk.

this is of course under perfect seeing In barbados, but  I still find 0.1 works best for me.

remember those calculators aren’t taking into account unsung lucky imaging with 10s of thousands of split second exposures.

1 minute ago, geoflewis said:

Do you mean 0.08" to 0.09" per px. Jupiter at say 49" / 500px = 0.1" / px not 1" / px - or what am I doing wrong please?

Yes sorry I typed it wrong I will go back and correct it to avoid confusion in the thread

16 minutes ago, geoflewis said:

Thanks Vlaiv, so I'm getting more and more confused and/oruncertain about my sampling with the C14 and ASI462MC camera. I've loaded a recent image into WinJupos which reads the image as 339.8 px and 0.1407"/px (see below image)

Dawes' and Rayleigh limit calculators (see below) give the max resolution of my scope (C14 dia = 356mm) at between 0.33" to 0.39", so allowing for min 2px ideal sampling will be half of those so somewhere in the 0.16" to 0.20" range.

If WinJupos is correct and I'm already sampling at 0.1407"/ px, then aren't I already oversampled?

FWIW I checked one of my images from last year with the ASI290MM + x2 TV PM and WinJupos gave me 0.9" / px.....!!

I'm really confused now, so please can anyone let me know what I am doing wrong with my maths?

My jupiters measure around 500 pixels with my current sampling with the 12” scope, I’ve found that about the ideal. So about 0.1”/pixel, Damian and GO are a bit higher than that around 6-700 pixels or around 0.08-0.09”/pixel but that’s with 14” scope and perfect seeing.

2 minutes ago, vlaiv said:

Quite simple procedure.

Take your Jupiter image as recorded (no drizzle, no binning, no rescaling) - but it can be stacked and sharpened (and it really should be for measurement precision).

Measure diameter of Jupiter disk on equator (there is actually quite bit of difference as I recently found out between measuring at equator and at an angle) and check current or rather at the date of recording, apparent angular diameter of Jupiter.

Divide the two to get pixel scale - and from that and pixel size - derive actual focal length.

Yes and to measure a simple way is to just crop the image in photoshop until it’s just touching the limbs the go to image size to see how many pixels it is.

though first make sure it’s rotated so the equator is level and wack up the mid level slider to expose the limb darkening enough to see the true edge.

alternatively win jupos can do image measurements precisely.

15 minutes ago, geoflewis said:

Hi Lee, I'm not sure about Chris using F24, but maybe he is. This is from his website...

All images were taken using a Celestron  C14  mounted on an Astrophysics AP900GTO mount.  A QHY 290M and a QHYIII462C cameras were used is these images.    RGB is done using a set of Chroma Technology RGB filters on a Starlight Xpress Motorized filter wheel.  Methane band images are done using a Chroma Methane Band filter (889nm  18nm bandpass).  UV images are done using a Astrodon UV filter.   Amplification is done using an Astrophysics Advance Convertible Barlow working at 2.0X.

So his amplification is 2.0x and the nominal FR of the C14 Edge (FL3910mm)  is F11, so I think more like F22, than F24 (depending on where he positioned the main mirror in his initial focusing), unless you have another source of info from him. It's still a lot more than the ~F12 that I've been using.....🤔

I now have the Baader x2.25 barlow with the removable x1.3 lens, to add to my image amplification toolkit, so lots of options to play around with.

Chris told my personally that hes working at f24, this was a few weeks ago.

Barlows never give the exact multiplication factor they claim and the adc spacing to the barlow will add a bit more, im sure hes measured jupiters disc in pixels to get a true value before telling me. as I do that with mine each time i change anything.

i hope you like the baader barlow, at least it wasnt too expensive, i bought it after seeing an amazing saturn taken with one, 

Lee

2 minutes ago, ollypenrice said:

Ah, gotcha! Yes, that would be a good idea. Thanks,

Olly

Though can’t tell what size the rings are from the listing so would need to ask to see if they are larger than your Altair 80 tube diameter.

4 minutes ago, ollypenrice said:

Thanks Lee, but I won't be guiding the 14 inch, which won't be doing DS imaging. You're right about a bit of planetary imaging, though. I've no idea what the current top camera choices are but it would be good to look into them.

 

Yes I know its for visual, but you said earlier in the thread you were looking for a way to mount your Altair 80mm to the top for wider views, so I thought these guide rings would be the easiest option as they have the correct curvature for mounting to the front and rear cells and include rails with sliding rings so you can balance it.

cheaper and more functional than buying another dovetail.

Lee

My  old 12" LX200 is still working fine on its original fork drive, but if it ever dies I will have to buy a 2nd EQ8 for it. 

you should do some planetary with the 14" once you have it mounted, the 12" is proving excellent for the task 

You can just see the Astro Engineering guide scope rings that I picked up as new old stock for from ENS for only £25.

It's a good idea to vacuum out the screw holes after de forking before you put the bolts back to avoid swarf going inside. the tinniest smear of grease on the bolt threads helps if you are going to be removing them a few times.

Hi Olly, I have a set of these for my 12" LX200 but looks like he has sold out of 12" & 14" versions

https://ensoptical.co.uk/index.php?route=product/product&path=126&product_id=13815

Though just found this rail and ring system on eBay which fit the 14" which include a cheap guide scope. If I had your scope I would snap these up fast 🙂

https://www.ebay.co.uk/itm/203925817273?hash=item2f7aed07b9:g:lvMAAOSwI9ViaByn&amdata=enc%3AAQAHAAAAsG%2FrUJ87uwu85svy6G%2FQ7RuVbCpcHjI0bg%2Bt1XxGIJriLvveM1KG3B7njz52%2Fbz0oURB5m9Cvn1mbdl2UL61Cam6yL9aDxG938i3SIO%2Fi%2Fuh2Eg7Ogb38hlNIZ6J272gpCrbQGMwk2cqxE4G0uPjRo%2Fx0osfTRUro3bKtOjC0vTrVv9Pi2UvTze0jmKOMTrEfPTyuT9wLJfj09N73MTUqCBsaJcJTYUd0Fc6j%2B7zDjza|tkp%3ABk9SR4St3NuHYQ

Lee

40 minutes ago, vlaiv said:

 

If you use ASI462 - and want to do IR imaging at 850nm, then following is correct:

F/ratio = pixel_size * 2 / 0.85 = pixel_size * 2.35

How about that? With 2.9um pixels you actually need only F/6.8 if you want to shoot IR at 850nm and above.

If you said someone that they need not go over F/7 for planetary imaging (example Jupiter at with IR pass filter) - they would say that you are nuts

 

Yes I do reduce my FL when using my 850nm IR filter and 889nm CH4 filter, though not by as much as that. I normally just take the spacer out of the Barlow. Oversampling doesn't bother me really but the 12" aperture isn't really enough to produce a bright enough image for using the CH4 at the same FL as with the other filters.

Id seen a talk by Cristopher Go when he was using the CH4 filter with his 290 mono and he would bin 2x2. but once he got the 462C he stated that it was so much more sensitive in IR that he doesn't need to Bin with it, for ease of use he doesn't adjust his FL as that would mean re focussing and be more time consuming. 

So all of his images are taken at F24 with the C14 at 8.5m FL

His CH4 images are still presented at a smaller scale, but I think thats because his 1.5x drizzle stacks his visible light captures but not the IR ones.

Saying that though I may still try taking the Barlow out altogether for the 850 and CH4 next time as ive not been happy with either of them compared to my IR742 which always seems to do a better job, and there isn't as much detail to capture in CH4 anyway

Lee

21 minutes ago, johnturley said:

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 

 

Hmm some mixed info going on there John, a 150 mm scope won't be able to handle as much magnification as a large scope anyway, so we have to be careful about recommending an optimal f ratio for a given camera.

but all depends what Barlow you would be using, its not like deep sky where you can match the camera to the scope, its more about matching the camera to the FL its operating at depending on the Barlow, or look at it the other way around adjust the focal length with different Barlows to match the FL to the pixel size of the camera.

I use both a 224 and 462 with my 12"SCT I have to vary the focal length with my Barlow spacing  depending on which cam im using. the 224 needs about 8000mm FL to get same pixel scale as the 462 at 7000mm FL.

20 minutes ago, geoflewis said:

Thanks Lee, I already checked it out, but it seems to be out of stock everywhere currently, so I'm not likely to get one in time for this year's apparitions. I'm going to play with the spacing of my existing TV barlows, to see if I can bring the mag down to nearer F17

I saw a used one the other day but can't remember where

15 hours ago, geoflewis said:

Hi Lee, this has been a very helpful thread, thanks. I also had a long and very helpful chat with @neil phillips this afternoon in which we covered a bunch of topics around optimising planetary imaging. He also says that I'm wrong to be imaging whilst undersampled, due to loss of potential resolution, so really I would be better to go back to a being a bit oversampled. We discussed some solutions to get me there with my existing gear, so I'm definitely going to try that again, particulaly in the run up to Mars oppistion next month. I guess watch this space.....🤔

https://www.firstlightoptics.com/barlow-eyepieces/baader-classic-q-225x-barlow.html

this is the Barlow I was talking about, gives 1.3x or 2.25x. but you can also adjust that further by altering the spacing

44 minutes ago, geoflewis said:

That's interesting Lee. I believe the rule of thumb is that FL should be x4-x6 pixel size in microns (@vlaiv has written the maths on this elsewhere), so as the 462 sensor is 2.9mn pixels, that gives a range of say, F12-F17. I only have x2 TV and x3 TV barlows, or x2 TV PM, so with the ADC in train those are going to push me well into the FL>20 range. I did experiment one night with the x2 PM, which magnification actually reduces (to about F20) when set back with the ADC, but I concluded that it was still too much. Maybe I should try that again. I have considered using the x3 barlow then binning the camera, but I'm not sure how that would turn out.

I'm not aware of the Baader Q turret (well I am now 😉), but that does sound like a sweet solution, so I'll check that out, thanks.

Yes I’ve read many debates on the 5x pixel size but others say 7x. But following Damian Peach’s example he’s normally working his c14 at around 7-8metres depending on the pixel size and likes to cover Jupiters disc with 5-600 pixels so that’s what I’ve been doing and have had good results. If it’s a poor night then I drop down to 6 metres, if it’s a good night then I go up to 7 metres.

Lee

29 minutes ago, geoflewis said:

Thanks Lee, I'm using the C14 at it's native F11, but the ADC pushes that up to between F12-F13, which is maybe a tad undersampled for the 2.9mn pixels of the ASI462, but I think introducing any barlow or powermate would be too much.

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

Thanks chaps, really quite chuffed with this one.

Lee

I guessed it was the 2nd image from the larger scale, to my eye the top image looks sharper

I briefly had an ADC in September to use on my 12" SCT but after waisting several nights with it I found that all the captures with the ADC were lacking detail compared to without it, I was 95% sure I had it adjusted correctly as the captures with it showed less colour fringing, but also much less detail, so I concluded that I either had a duff one or the brand I bought was just crap but was able to return it. I don't have much patience with things like this and not enough clear nights to experiment

 I also tried on Saturn where it did remove the colour fringing, but I feel Saturn is too low for sharp visible light images at the moment anyway so prefer to just image low planets in IR

Ive been getting what I think are very detailed Jupiter images without it so am in no rush to get another one.

Lee

Nice images Neil, when you say recent brightening , how recent do you mean? I just looked at an IR image I took on the 6th but the whole pole looks dark in that one.

Lee

Nice set Geof, what f number are you working at approx? 

Lee

Just getting around to processing some data from the last month, captured this image of Jupiter on OCT 6th centred on 22:54UTC 

Meade 12" LX200GPS + 2.5x GSO Apo Barlow @ f25   

QHY5III-462C

9 x 60sec captures derotated each one was best 40% of 10,000 frames.

Not sure I will be able to improve on this image from the UK, Jupiter is now past its best for this apparition and I dont think the seeing gets better than it was this night in the UK. I may be able to get another 10% out of it if I keep trying different processing, but pretty much hitting the seeing wall now, at least with the 12" scope.

Ive taken so many catures of Jupiter in the last couple of weeks but not got around to processing many of them. Here is a single capture from the Oct 11th taken in Infrared under pretty good seeing.

have some hints of speckling in the north Tropical region which Is first time ive resolved that, so not bad for my UK location

Meade 12" LX200GPS @ f21

QHY462C + Astronomik IR742 filter