johnturley

8 hours ago, inFINNity Deck said:

Hi John,

 I do not mention chip-size simply because it is irrelevant. If you do not want that black space around the object, simply crop it in the post-processing. None of the planetary images I show on my website are shown at the actual image size they were imaged at, most of them have a larger background than original, while almost all have been resize by that 200% I mentioned before in order to make them a decent size for viewing.

The point I try to make is that, when using an optimal focal ratio, the exposure times go down significantly. Had the image been made at about f/9, the exposure time would have been 4 times as low, resulting in a higher frame-rate and thus more data in the same time-span (and thus a better signal-to-noise ratio had the same percentage of frames been stacked).

Nicolàs

 

You state that the chip size is irrelevant, but the general consensus on this site appears to be that for planetary imaging you need a camera with a small sized sensor, and that digital SLR’s are not ideal for planetary imaging due to their relatively large sensor size. If this were not the case, then why would some observers have 2 or more cameras one with a small sensor for planets, and one with a larger sensor for deep sky objects, if the camera with the larger sensor would suffice just as well for both.

Having said that, I accept that for a given optical arrangement, the size of the image on the sensor will be exactly the same regardless of the size of the sensor, or the degree of cropping used. It appears to be that the software used for image viewing just displays the images taken with a small sensor and/or cropped as being larger, which makes them more aesthetically pleasing, and easier to process. I would love to see a large detailed planetary image taken with a digital SLR, using no more than a 2-3x Barlow for amplification, which you and some others say is possible.

Some observers are also of the opinion that around 2x oversampling gives better results than the theoretical optimum of around 3x the pixel size. I suppose it’s a bit similar to saying that with for example a 6-12in aperture telescope a magnification of about 50-100x is capable of revealing all the planetary detail that is there, but most observers find under good conditions, using a magnification of 200-300x more aesthetically pleasing.

I will however try doing some imaging closer to what should be the optimal focal ratio, using additional cropping or the drizzle function in Autostakkert to increase the image size to see whether it does give better results

John  

Last night had my best view of Saturn this apparition, and look my first image, taken through my Esprit 150 using a 2.5x Powermate, and processed in AutoStakkert and Registax, and a bit of polishing in Lightroom.

P.S. I have processed another Sharpcap video since this morning, and attach the latest one, which I think is somewhat better than the original.  

John 

7 hours ago, inFINNity Deck said:

Hi John,

good point, sure there is a difference, so let's have a look at the maths.

Pankaj plans to use a 10" f/5 Newton with 2x Barlow and his Canon with 4.3 micron pixel-size. That combination yields a resolution of 4.3/(25.4 x 10 x 5 x 2) x 206.3 = 0.349"/pixel. Currently Jupiter is about 44.36" in apparent diameter, so that is 44.36 / 0.349 = 127 pixels on his camera. Now he should be imaging between f/12.9 and f/15.9, so should be using at least a 2.5x Barlow (f/12.5). Using that Barlow he would get a planetary diameter of 127 x (2.5/2) = 159 pixels (3 x Barlow would make this even 190px). In my set-up this would become about 204 pixels, so indeed significantly larger (about 28% more than with with the 2.5x Barlow), but not a whole lot, and even insignificant if he would use a 3x Barlow. The diameter of Saturn with rings is approximately equal to Jupiter at the moment (44.14" vs 44.36"), so that planet would give the same results. The planet itself (i.e. the globe of Saturn) is of course quite a bit smaller, that would become 67 pixels would Pankaj use a 2.5 Barlow (81px when using a 3x Barlow).

Above images of Mars were taken on 26 December 2022 while it was only 15.35" in apparent diameter, so a third of current Jupiter and Saturn and thus only about 75 pixels in my 3 x [pixel-size] set-up, so approximately the same size as the Jupiter that Pankaj can image with his set-up.

Nicolàs

Nicolàs

You make no mention of sensor size or capture area, I don’t know by how much, if at all, you can crop the capture area with the Canon 1200D, but it will be almost certainly less than with a dedicated planetary camera. So if Pankaj uses his 10" f/5 Newton with 2x Barlow and his Canon 1200D (Aps-C sized sensor 24x18mm), using no more than a 2-3x Barlow for amplification, then I think that he will be disappointed with the resultant small image size.

My first attempts at imaging with my ZWO ASI 462 Planetary Camera (which has a sensor size of just 5.6 x 3.1mm) through my Esprit 150 weren’t that great, as I didn’t appreciate that you need to crop the capture area to get an image that appears to be of decent size.

My first attached image taken in August 2021, shows the result of an uncropped image at the native f7, which isn’t actually far from what is supposed to be the optimum of 3x the pixel size of 2,9 um. Although the size of this image can be increased using post processing software, I found that if I tried to do this by more than 2x, the results weren’t great.

The second attached image was taken with the same setup, taken in October 2022, but using a 2.5x Powermate, giving f17.5 (nearly double what is supposed to be the optimum), and cropping the capture area, giving a much larger apparent image of reasonable size. I think that you will agree that the second image, which shows the GRS, is much better showing far more detail.

The third attached image taken in August 2020 shows what I achieved using eyepiece projection (I think that I used a 12.5mm Plossl) with a Canon 6D full frame digital SLR,  if I had just used a 2-3x Barlow, the image size would have been much smaller. At the time Jupiter was quite low down, and it was more difficult to focus through the camera viewfinder. 

John 

3 hours ago, inFINNity Deck said:

Hi John,

Please note that there is a difference between "a decent sized image" and an image with maximum detail. The formula 3 x [pixel-size] (or 3.7 x [pixel-size]) gives the focal length at which the maximum detail is recorded. Going above this means that no additional detail is recorded while exposure times go up drastically (quadratic with the amount of oversampling, so going from a factor of 3 to a factor 6 increases exposure times by a factor of 4!). It is for that reason that I stick to the formula and create a decent size after processing by using a bicubic resize of 200%. I have been testing this with a ASI290MM and found no advantage detail-wise when compared to the ASI174MM that I normally use. The pixel-size of the ASI174MM is twice that of the ASI290MM (5.9 vs 2.9 micron), so I resized the ASI174MM images by 200% after stacking to make them the same size in below image (all imaged at f/20 with a C11 EdgeHD). The image at the far right is the same as the one at the centre, but with additional sharpening (bit too much to my liking, but it was to see what happens in the image analysis):

 

 

Nicolàs

Nicolas

But you are using a C11 Edge HD (focal length 2,800mm), I think the situation would be somewhat different for someone using a much shorter focal length instrument, say 500 - 1,000mm, or a much larger sixed sensor than your ASI 174, or ASI290, as with a digital SLR.

John 

12 hours ago, John said:

Tonight Iapetus is looking a little brighter than I would have expected, again. It seems close to Rhea in brightness and certainly brighter than Dione although the latter pair are quite a bit closer to Saturn itself so will be affected by it's glare. Tethys and Enceladus are too close to the planet to discern tonight. Dione is quite tough to spot with the 4 inch refractor that I'm using tonight. 

 

 

 

I found Dione difficult last night even with my 14in, as mentioned before I put it partly down to my deteriorating eyesight, although I have had a cataract operation in my (right), observing eye. Also I was viewing Saturn through some thin high cloud, and there was a not far off full moon not far away.

John 

15 hours ago, inFINNity Deck said:

Hi Pankaj,

 

In short it comes down to that the focal ratio can be about 3 x the pixel-size of the camera. If I understand well the Canon 1200D has a pixel-size of 4.3 micron, so optimal sampling is done at a focal ratio of about 3 x 4.3 = f/12.9. Theoretically you could go as far as 3.7 x 4.3 = f/15.9, but seeing will limit this rule to about a factor 3 (at least at my location, not sure about yours in India). For your scope this means you could use a 2.5x or 3x Barlow. There is no need to guide, I have seen plenty examples of great planetary images using 'manual driven' dobsons. Please note that exposure times go up with larger Barlows.

 

If you want to use the Canon, I suggest you capture in highest resolution and maximum frame-rate. If that means you have to image separate files instead of AVI or other movie-format, you can use PIPP to create a SER-file from those separate images, which then can be processed in AutoStakkert!3.

 

If you are doing planetary imaging with a Canon 1200D (APS-C) sized sensor, I think that you will need to use eyepiece projection to get a decent sized image, a 2- 3x Barlow just won't give sufficient amplification. If the initial image size is too small, then you can't get sufficient decent alignment points in processing software such as AutoStakkert and Registax, a tiny image also makes initial focusing more difficult. 

When I used my Canon 6D (full frame sensor) with my 14in Newtonian, I needed to use eyepiece projection with a 12.5mm Plossl to get a decent sized image with Jupiter, and a 9.7mm for Saturn and Mars.

I now have a ZWO 462 Planetary Camera, which has 2.9 micron pixels, but unless viewing condition are particularly good, I prefer to image through my Esprit 150 (fl 1050mm). According to the formula, the optimal focal ratio should be 3 x 2.9 = f8.7, but to give a reasonable image size even with Jupiter, I need to use a least a 2.5x Powermate giving f17.5. 

One observer on this site produces excellent nice sized planetary images through his C11 (fl 2,800mm ) and ZWO 462 at f20 (2x Barlow) , or even f25 (2.5x Barlow).

John 

11 hours ago, johnturley said:

Looking at Saturn last night, I also could see Iapetus quite easily along with Titan, Rhea, and Dione. I could also make out what looked like a brightish 'moon' to the right of Titan (as seen in a telescope giving an inverted image), which according to Stellarium, roughly corresponded to the marked position of Hyperion,. However as it appeared only about a magnitude fainter than Titan, and brighter than Iapetus and Dione, I assume that it must have been a star (not shown as such on Stellarium) and not Hyperion. 

Did anyone else see this. 

John 

Are their any experts on Stellarium out there, that might know whether it is possible to reduce the limiting magnitude of satellites, such as those of Saturn, displayed in 'Ocular View', so that in the case of Saturn for example it only displays the original pre-spacecraft 9 satellites, and increase the limiting magnitude of background stars stars displayed.

I find it confusing that 'Ocular View' in Stellarium in the case of Saturn, displays lots of approx 15th magnitude minor satellites, which are not visible in amateur telescopes, but did not display a 12th magnitude background star that can easily be confused with a brighter satellite. I know that Stellarium does display background stars in Ocular View down to a certain magnitude, as the other week it did display the 5th Galilean moon that Jupiter appeared to have, (which was actually an approx 6th mag star in Aries), but did not show the 12th magnitude star in Aquarius, which was close to the predicted position of Hyperion.

John 

35 minutes ago, John said:

 

I've never seen Hyperion either but I have seen Enceladus quite a few times when it is towards it's maximum elongations from the planet and it's rings. Not last night though.

 

Me too, I don't know whether its a question of increased light pollution, or my deteriorating eyesight, or a combination of both, but in the 1970's with the 10in Newtonian I had then, I used to find Rhea, Tethys, Dione and sometimes Enceladus easy to spot. In recent years however, even with my 14in I've found Dione and Tethys quite hard to spot, and not seen Enceladus recently. 

For most of the 1970's though, Saturn was quite high up from the UK, so hopefully visibility of the fainter satellites will improve over the coming years, as Saturn moves higher up, and the near edgewise rings in 2025 will also help.

John 

17 minutes ago, IB20 said:

There’s a mag +10.5 star listed in SkySafari.

Yes, almost certainly that star, thought it appeared far too bright to be Hyperion, which incidentally I've never been able to see visually.

John 

Looking at Saturn last night, I also could see Iapetus quite easily along with Titan, Rhea, and Dione. I could also make out what looked like a brightish 'moon' to the right of Titan (as seen in a telescope giving an inverted image), which according to Stellarium, roughly corresponded to the marked position of Hyperion,. However as it appeared only about a magnitude fainter than Titan, and brighter than Iapetus and Dione, I assume that it must have been a star (not shown as such on Stellarium) and not Hyperion. 

Did anyone else see this. 

John 

Observed Saturn and Jupiter last night, viewing conditions were not very good and rather unsteady, I was unable to make out Cassini's Division on Saturn, but moons Titan, Iapetus, and Rhea were quite easy to spot, plus fleetingly I could glimpse what I think was Tethys, based on Stellarium. 

On Jupiter I was able to spot the shadow transit of Europa, but only when the shadow got to near the middle of the Jovian disc, I find shadow transits of Europa harder to spot than those of Io and Ganymede. 

John 

On 22/08/2023 at 19:48, mikeDnight said:

 

 The FC100DC was an awesome scope but I eventually succumbed to reviews about the DZ by Daniel M on CN. It was an emotional wrench for me to part with my DC and wait for a DZ, which arrived on a slow boat from Japan. During the month without an FC I had to resort to using one of those reflector thingies, a 10" F6. Finally my DZ arrived and it was simply gorgeous. I know I'm an oddball for preferring these small scopes over larger ones, but even for those with larger aperture reflectors, I doubt anyone would be disappointed by having a DC, DF, DL, or DZ in their optical arsenal.

Mike

Did you notice a significant improvement in the planetary performance of the 100DZ over the 100DC, I'm inclined tp prefer the DZ, but I might consider the cheaper DF if there was negligible difference in the performance compared with the DZ. I assume the DF would be similar to the DC,  and I did want a model with the larger focuser as I have several 2in eyepieces. Since the DF is f7.4 rather than the f8 of the DZ, I assume the tube will be about 6cm shorter, would this make the difference regarding aircraft carry on baggage. On the other hand I might not end up taking the scope on holiday anyway, in which case the DF would have not have any advantage over the DZ for me apart from saving about £600.

John 

On 22/08/2023 at 17:32, JeremyS said:

What I am trying to convey is that there appears to be a shortage of FC 100DZ, due to a production delay in Japan. I see prospective US purchasers are drawing a blank lately. So if you are interested in one, then contact a UK dealer to check on current status and the delivery time. 

The delay was announced last September: https://www-takahashijapan-com.translate.goog/ct-news/topics/22ix22_info.html?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp

Anecdotally its due to the glass for one of the lens components being unavailable.

According to FLO's website, they now have 2 FC 100DZ's in stock, so I assume Takahashi must have now overcome the problem of shortage of the relevant glass.

Unfortunately RFVO's (and also Wide Screen Centre) website does not state whether they have them in stock, but I am assuming  there must be a reasonable  supply of stock available at present. 

John 

Astro Trails are now saying on their website that there is limited availability on all their existing Mexico Eclipse Trips, although they they have now added on a 4 day 'Mexican Quickie', thought I would mention it anyone is still considering booking a trip. 

John 

I downloaded Registax 6 on my Windows 10 laptop a couple of years ago no problem, I have MacAfee antivirus 

John 

1 hour ago, JeremyS said:

Suggest you email them for accurate availability info. 
 

If I decide to get one, I would probably go to Rother Valley Optics who are nearby so that I could pick it up the scope in person, and avoid the risk of any damage or mis-collimation due to rough handling by the courier. I might also ask whether they would do a trade-in with my CPC 9.25 (which I purchased from them), although I suspect that any trade-in price would not be very good compared to what I could sell it for privately. 

I picked up my Esprit 150 direct from Es Reid after he had checked it over, so that I could be sure that this did not happen.

John 

48 minutes ago, JeremyS said:

The Tak FC 100 DZ is a wonderful and compact, light instrument. I don’t think it would be airline portable though, unlike the DC. The dewcap retracts a bit, both not enough to make it short enough.
FLO had a DZ for sale until recently, for a surprisingly long time, but I think they are unobtainable for quite some time to come. They still have 3 TSA 120s in stock though (!)

 

FLO are still stating on their website that it can be carried out on most commercial flights, but I've had this contradicted from a couple of sources.

They are stating currently out of stock, but available in 15-20 working days. 

Takahashi FC-100DZ (OTA) tube only with 50.8/31.75 adapter | First Light Optics

17 hours ago, John said:

I have a Starwave 70.  I've been very impressed by what it can do. Taks show you everything that the given aperture can show and their images are very, very refined. They are still subject to the constraints that aperture brings though in terms of light grasp and resolution. 

I bought a Tak 100mm F/9 a few years back, probably for reasons similar to those you might have - curiosity being the main one. It has turned out to be exactly what I hoped and expected - a truly superb 100mm refractor for visual use (which is what I do). No more, no less 🙂

My Skywatcher ED120 goes fainter, splits tighter double stars and shows a little more planetary and lunar detail than my Tak 100, but then it should with 20mm additional aperture to play with.

 

That's interesting, I have for some time been tempted by a Tak 100 DZ, which I would be able to fund if I sold both my Celestron CPC 9.25, and Explore Scientific 127 FCD 100 Refractor, which to be honest I don't use very much these days. In particular the CPC is getting rather heavy for me to move around these days at my age (73), plus my wife keeps pressurising me to reduce the number of telescopes in the conservatory (my 14in Newtonian and Esprit 150 are in my observatory shed).

According to some posters the Tak fluorites perform like magic, permit 100x per inch of aperture to be used, and outperform other scopes of significantly larger aperture, in particular on planets.  So like yourself I have been curious as to how one would perform, for about the same price as the 100 DZ I could obtain an APM 140 Refractor, which would almost certainly be superior to the ES 127, but less portable. 

The Tak 100 DZ, would however be a very high quality, plus much lighter and more portable instrument, and according to the spec I would be able to take it in the cabin on aircraft, although I have heard from a couple of sources that the latter in not actually the case.

John 

Arrived a few days ago from Amazon, a Reesibi Air Duster.

Reesibi 90W Electric Air Duster Blower, Strongest 90000 RPM Compressed Air, Strong Blowing Force, Brushless Motor, 7500mAH, for PC, Keyboard, Car and Home Cleaning, Replaces Compressed Air Can : Amazon.co.uk: Stationery & Office Supplies

I had been thinking of getting one of these for some time after reading a favourable review (I think on Cloudy Nights), with the intention of it replacing my Kenair Compressed Air Duster. What tipped the can however, was that I found out that the cost on Amazon of a replacement air cylinder for the Kenair, had gone up from around £17 to £24, plus Amazon had 30% off the price of the Reesibi, reducing it from £49 to £37, so I bit the bullet.  

I'm quite impressed with it so far, it is cordless with a built in rechargeable battery, and the air jet (which has 3 settings) is much more powerful than a hand blower, and almost as strong as the Kenair, but spread over a wider area. I used it successfully on my 14in Mirror yesterday, and unlike the Kenair, you don't have to worry about it depositing propellant (which is difficult to clean off) on the optics, if it not held vertically. Another risk with the Kenair, is that some years ago with an earlier model, the metal jet became detached and shot out at speed, which could have smashed a mirror or objective. The Reesibi unit will also be useful for drying off my mirror after a wet clean, last time I think I depleted about half a Kenair cylinder doing this. 

It comes with several attachments, including a USD charging lead and a brush attachment, which I shall not be using on optics, but may be useful for cleaning computer keyboards.

John  

20 minutes ago, Space Cowboy said:

Nicely captured Simon! Too much cloud here in Cheshire.

Same here, had planned to view the GRS and Ganymede transits, but clouded out.

John 

Just now, Ulyana said:

which ones are you sure of?

If you look on First Light Optics website under ZWO Cameras, you can view the specifications of each model they stock, or drop them a line on questions@firstlightoptics.com

John 

1 hour ago, Ulyana said:

533 camera can handle such a task? or is 178 better? And what kind of lens can be used to shoot the whole sky?

Some ZWO cameras come with an all sky lens, not sure about the models in question.

John 

28 minutes ago, Mark2022 said:

ISO and Exposure settings, John? The longest exp setting I can get is 1/30th with video. Then again, I believe we don't want long exposures anyhow BUT, dropping exp time makes the planet even dimmer so then, I suppose, it's upping the ISO? However, that then introduces more noise so....  ?

I haven't used my Canon 6D digital SLR for planetary imaging since getting a ZWO 462 Planetary Camera in 2021, if I remember rightly I think that I used around ISO 800 or 1,600 at 30 fps using eyepiece projection with a 9.7 mm Plossl.

You get a lot more control over the settings with a dedicated planetary camera.

John 

14 minutes ago, JeremyS said:

Partially clear in Cheshire again last night, tho some thin high stuff around.

Meteorcam captured 44 meteors of which 12 were Perseids 

I understand that the normal sporadic rate is supposed to be about 10 meteors per hour, so based on this the Perseids did not put on much of a display. 

John  

11 minutes ago, Mark2022 said:

So here are the two photos I took of Jupiter and Saturn the other night. Happy to capture anything at all but looking to, eventually, achieve what BGazing has above. How? I have no  idea as yet. Perhaps I'll get closer with the SV305. I  can't even remember the optical train for these photos. Whether I used the 9.7mm eyepiece projection (I did try at some point thru the night) or whether just at prime focus with either the 2x or 3x barlow.  I should keep notes. If you heard the audio on the video captured, you'd understand! 🙂

Any and all additional advice, appreciated.

 

 

With a digital SLR you will need to use eyepiece projection to get decent sized images that you can work on in processing programs, a 2 or 3x barlow won't give sufficient amplification, your 9.7 mm eyepiece, or with an APS-C sized sensor a 12-15mm eyepiece should work quite well.

John