Astrograph that is also good for visual planetary?
Hi all
I was thinking of setting fire to a lot of money but then I figured getting into astrophotography is probably a more efficient way to ensure my continuing impoverishment.
Currently I have a fairly big Dob that only really comes out for Deep Sky trips. It would be nice to have something smaller that is good for Planetary viewing (ie, not having to look through such a large column of air) and also for venturing into astrophotography. TBH, it would be an astrograph first, and a visual scope second.
I'd be looking for something in the 4-6" range I think.
In my reading I've seen that you want to have an Apochromat over an Achromat, and a triplet over a doublet. But at that price, wouldn't a 4-6" reflector be cheaper? I don't mind the look of diffraction spikes. But do the changes in collimation from night to night mean that data gathered on different nights is not compatible with each other due to subtle geometry shifts in the image?
Or would a Cat/Mak style design be better because it's smaller and the shorter tube design has less leverage on the mount as the ends are fairly close to it's own centre of gravity?
I live in the city, so the kind of photography I'd be doing would be narrowband or planetary, methinks. And the portability of a smaller scope is appealing.
I know most people recommend a small 2-3" refractor for starting out because the mount issues will be less, but I fear I may not be happy with such a small scope for visual. I'm considering a Skywatcher AZ/EQ6, depending on the weight of the scope I settle on.
If you want portable eq 6 is a little heavy whereas the eq 5 is a nice weight, for me at least.
On the basis of what you get next will not be the last I suggest a heq5 and a 6 inch reflector and a dslr.
The six inch reflector is underestimated but I found mine was great for visual and not bad for AP.
However if you want to spend go for a skywatcher 100 mm triplet and an eq6 ... knowing you will always want the 150 mm.
But if you start with a six inch reflector and sell it later for half what you paid you wont lose much...I would still be using my six inch but it needs a rebuild so I went 8 inch reflector and a 80 mm triplet.
Good luck I dont think there is an easy answer.
I will say using a dslr in Sydney has turned out way better than I expected.
Good luck.
Alex
I’ve just started astrophotography recently after a year of visual with my 10” dob
I didn’t want to spend too much money so I put together a great little kit which gives me great all round imaging of stars, DSO’s , planets and moon
I have a Bintel 150mm F6 reflector OTA with some mods 8x50 RA finderscope and dual Crayford focuser approx $350
A Sky-Watcher HEQ5 Mount with power supply approx $1350
I am borrowing my wife’s Canon 600D DSLR $Nil
Adapters , Barlow and Powermate approx $650
As a visual scope it’s actually better than my 10” dob,really crisp views, 2 minutes to collimate
As an Astro scope it’s fantastic , I have imaged M42 , bright stars, clusters, Jupiter, Saturn, Mars and the Moon
The specs for this scope mention it’s only useful for planetary and lunar imaging but I have imaged nearly everything in the sky which is in the capabilities of this scopes specs
I won’t be upgrading to a refractor for some time yet as the dollars don’t warrant me spending that type of money as a newbie to astrophotography
I'm a complete newbie to AP (my gear is only about 6 weeks old) so this advice may or may not be useful!. I started years ago doing visual with an old cheap Tasco 125mm Newtonian. It's mounted on a wooden tripod that vibrates so much it must be made from matchsticks. It was a source of frustration and only had limited use. In the last year I've been doing some photography with a Canon DSLR and lenses and then recently decided to do it properly.
I spent several months researching, initially quite certain I wanted a reflector of some sort, but the more I read the more I realised a refractor was the way to go. I ended up getting a Skywatcher Esprit 100ED which is a f/5.5 apochromatic triplet. It comes with a 2 element field flattener and all attachments necessary for my Canon DSLR. I don't have much to compare it with but I must say I continue to be amazed at how good the images are. My Canon has a crop sensor (22.3x14.9mm) and the stars are round and sharp to the edges of the field and absolutely no chromatic aberration. As an example I took the attached image last week and it is the full field of view with no edge crop. I was talked into buying a SW EQ6-R Pro as the mount which is probably overkill for the ATO but one day I hope to get something with a longer focal length (maybe a large aperture Ritchey-Chretien if my bank account ever recovers).
The setup so far seems really good for DSO but I guess not the best for planetary although when Mars get closer I will swap out the DSLR for my guide camera (ASI 120MC) and a 2x Barlow and see what happens.
I've got to say, if your budget can stretch to an apochromatic triplet you won't be disappointed.
As an example I took the attached image last week and it is the full field of view with no edge crop.
See, I'd be very happy with that. The stars are very sharp, no fringing.Admittedly that is a fairly bright object (Omega Centauri, correct?) but that's down to the mount and sub length I guess. Did you have to do anything in post, or is that pretty much how it looks?
I wonder how much better that image could possibly be given a premium scope like a Tak? I can't see much room for improvement, but then I don't know much yet so perhaps I can't 'see' yet.
I just read that the diffraction spikes makes it difficult to combine data from different nights - I assume because the spikes may not line up two nights in a row. If that's true, it would make the reflector less attractive for me, I think.
The stars are very sharp, no fringing.Admittedly that is a fairly bright object (Omega Centauri, correct?) but that's down to the mount and sub length I guess. Did you have to do anything in post, or is that pretty much how it looks?
Yes it's Omega Centauri (small steps, easy targets ). This was 30x 60 second subs at 800 ISO. Very little processing, just background balance, a histogram stretch and increased saturation to bring out the star colours.
I just read that the diffraction spikes makes it difficult to combine data from different nights - I assume because the spikes may not line up two nights in a row. If that's true, it would make the reflector less attractive for me, I think.
It's fairly easy to mark the orientation of your camera on the focuser so alignment is consistent and stacking software will compensate for that anyway (unless it's a long way out).
That Skywatcher Esprit 100ED of Kevins does look pretty impressive though and fast enough for AP.
To capture galaxies and smaller DSO's you really need to have a focal length over 1000mm, which means a slow refractor, Mak, RC or a larger but faster newt. For starting out in AP I think you should try and keep under f6 or you will have to go the whole hog with auto guiding etc to get enough exposure time.
Hi Markus,
I have a 6 inch Tak newt, AWESOME for AP and Visual! Really high quality views and images! If i wasn't imaging with it id be looking through it, better than a c8 IMO. BTW any rotation is awful for AP as you will have to crop to where the data overlaps, so just avoid rotation in general.
The Esprit are excellent DSO imaging scopes in their focal length brackets IMO, but when it comes to planetary, it’s all about focal length. Certainly when it comes to planetary imaging. And that’s where a second scope comes in handy
There is no perfect scope. Some are more suited to certain objects than others.
The Esprit are excellent DSO imaging scopes in their focal length brackets IMO, but when it comes to planetary, it’s all about focal length. Certainly when it comes to planetary imaging. And that’s where a second scope comes in handy
There is no perfect scope. Some are more suited to certain objects than others.
Does the image suffer if a faster scope is extended the use of powermates into more usable ranges?
Wouldn’t imagine so...a number of folk in this forum produce excellent planetary images with fast-ish newts.
Visually, it’d probably be imperceptible. The challenge for planetary detail is aperture == resolution. That’s why most folk are using SCTs or newts.
Then the eternal challenge is the seeing. Imaging at 550mm focal length (Esprit 100, I also have one) is a different kettle of fish when it comes to detail than discerning fine detail on Jupiter and Mars.
Just noticed the large Dob in your sig...use that on the planets...if that doesn’t show you good detail (when we’ll collimated) then try again when the seeing improves.
FWIW, planetary imaging wants for around f/20 for the current crop of planetary cameras, I’d imagine that’d be good visually also with your scope...would knock the brightness down a fair bit and help the eye.
I do get good detail (much better than my 8"), but not on the level of some of the images I've seen posted here. So far I've been happy with better views, but given what I've seen others post, I have a nagging feeling that there is room for improvement, and a number of variables to try to improve on.
I Imagine I could probably do planetary with my big dob if I got a tracking platform built for it - it's not like drift is an issue at those shutter speeds. With a 5x powermate it could be happiness n that department for the moment.
mo·ment
ˈmōmənt/Submit
noun
1.
a very brief period of time.
As has been mentioned, I’d suggest that you’re not going to get the same level of planetary imaging from a 4-6” telescope than you will from anything larger.
As Dunk says, aperture helps with resolution but it also helps with shutter speed and being able to collect enough data to be able to push the processing further before image breakdown.
The seeing conditions in Melbourne of late haven’t been great so that will have an effect and the mirror on your 16” GSO is reasonably thick so cooling it down takes quite some time.
If you want to do widefield DSO then a 4-6” refractor is definitely a good way to go. If you’re interested in better planetary imaging then either getting an EQ platform or installing ServoCat on your dob is the better way forward.
Yep. Thinking I'll make a platform for the Dob, then go a 5x powermate with the Canon in 4K mode, which gets me;
FOV: 8.39' x 4.42'
Resolution: 0.12"/pixel
Area: 37.1 sq'
Focal length: 9000mm
Focal ratio: f/22.5
Hopefully that will be enough. Of course, it's only half what's possible with a C11 EdgeHD, but when I look at spending maybe $700 for a powermate and bits and bobs to make a platform for the dob, compared to $11,000 for a C11 EdgeHD and Losmandy G11, I think maybe common sense must prevail.
Markus, I see no good reason why a C11 would be preferable over your Dob if you get it tracking, besides portability. But it’s not a C11 fits under the arm anyhow.
Incidentally, the Edge HD with its correcting lenses gives better views over a conventional SCT when viewing a wide (for a SCT!) FOV, but brings no advantage to the on-axis image like when viewing/imaging planets.
It’ll be interesting to see how you get on with your 5D MkIV, obviously that’s no entry level camera the high megapixel count is not necessary for planetary as the objects are rarely large, but the higher the frame rate the better.
If you're thinking of an SCT maybe grab one thats fastar or hyperstar compatible. It'll give you f/2 when you want to image DSO and f/10 when you want to view or image planets.
If you want to image planets you should get a small sensor cam, my zwo 120mc was only a couple of hundred $ and well and truly beats my 1100d for image scale.
). This was 30x 60 second subs at 800 ISO. Very little processing, just background balance, a histogram stretch and increased saturation to bring out the star colours.
the high megapixel count is not necessary for planetary as the objects are rarely large, but the higher the frame rate the better.
