What imaging scope with a dslr?

[newbie alert]

What do you use for imaging and why..trying to understand what all the APO,TRIPLET,QUAD..ED.. etc is for and their uses over one or another..

Fire away..

[cjdawson]

I use a Meade LX-90.  Why, because I own it already and it cost me a small fortune, so can't afford to replace. ;-)

 

Honestly, for my needs it's a great scope.  It's a jack of all trade, but that does mean master of none.   The optics are great for visual work.

For imaging, the F/10 can be easily exended to F/20 using a barlow for planetary imaging.  And indeed F/30 using my Powermate.   These combined with a webcam can be used to produce some great images of planets and the moon.

 

For DSO's I piggy back and ST-80 which I use as a guidescope.  Then attach a DSLR to the main scope. With the wedge, the mount is EQ, so long exposures are possible and I've been able to get 5 and 10 mins subs without any problems (well other than the tonne of problems that I've been working on and trying to solve)    Using a focal reducer, I can get it to image at f/6.3  and f/3.3 (not tried that yet though)  which means that I can get more light gathering capability.  I don't think that the f/3.3 reducer will work with my DSLR though.

 

The problems that I've had to overcome since I first bought the scope are a rather long and expensive story.

1. Dew - made a dew strap from nichrome wire and used a vellman kit PWM as a controller.   I now have two of these, one for the main scope and one for the guide scope. To keep my optics crystal clear.

2. Wedge - This does two things.  One, it makes my mount an equatorial mount suitable for photography.  Two, there's a plate attached permanently to the bottom of the fork mount, so the aluminium thread isn't likely to get stripped through use.

3. Bahtinov mask - for focussing this is a must have for everyone.

4. ST-80 piggy backed.  I used this for guiding.

5. Starlight Express Superstar - still waiting for first light.  This camera is very sensitive to low light and I've had it register mag 8 stars whilst the mount was static.  I'm sure that I can go lower for increased exposure time.    If the camera can't see the star, it can't guide.

6. Canon 70D (unmodded) - it's a good DSLR that I can use for daytime and nighttime photography.  Rather than mod it, I would be looking to get a camera specifically for Astro imaging.  With laptop, it can be controlled direct from that, and the images downloaded directly too.

[newbie alert]

I own a 8inch sct with a 6.3 focal reducer i can get orion and andromeda just in the frame..rosette ,m45  etc are way too big...so was thinking of getting a 80mm refractor for dso..

Ive got a 80mm guidescope but once piggybacked it seems clumsy and side heavy if its on its side....didnt know you can get a focal reducer lower than 6.3 for them...might be another option!

[xtreemchaos]

I use a ed80 for solar ,moon and DS, I use also a AR127L non APO for close ups ,planets, solar and it takes cracking images of the moon with my 1200d, its all about what works for you, I also have a 200p newt what I use for both vis and imaging with a CC.  ive found what I'm happy with, but ive had a tec 150 on mind for quite a while, I might have to give in to temptation at some point.  clear skys,  charl.

[Stub Mandrel]

The Skywatcher 130P-DS is hard to beat for twice the price, even with a coma corrector (which helps make sure the stars are perfectly round right to the edges).

It's a light reflector with reasonable light gathering power and an excellent mirror that gives results even on light mounts.

A hole thread of happy owners showing off what it can do:

 

[SonnyE]

When I began looking, I was looking at a large refractor, Celestrons 150mm (6") on and AVX mount.

As I refined what I wanted to actually image, Nebulae, my research took me what I have, an 80mm Triple APO in Carbon Fiber.

My original intention was to use my DSLR. But as I looked deeper into everything, I realized I wanted a cooled CCD and to not wear out my DSLR any faster than I already was. (Over 50,000 shutter actuation's the first year.)

So when I decided to pull the trigger on my Astro equipment I got an Orion ED80T CF telescope, an Orion G3 color CCD camera, and a Celestron AVX mount. And a lot of other stuff after the fact. As it were, I was really bustin the budget. But I wanted to get into the Astrophotography for myself. So I got the best I felt I could at the most reasonable price. My intention was to buy once, cry once.

The hardest part has been the learning curve, and a smattering of equipment failures. But here a year and a half later I'm finally getting to where I dreamed of back in the beginning of 2015. Still refining my work, wishing for an electric focuser, but really happy after the bugs and failures.

[Thalestris24]

Hi

I have a 130pds though not used it in a while. Also a smc Takumar f4 200mm and a TS 80mm f6 triplet Apo. Short focal lengths are great for dso, easy to guide. Reflectors and apos are great for colour correction so no chromatic aberration.  The 130pds was pretty cheap. 2nd hand vintage lenses are cheap. Apos are expensive, but let's face it, nice to have!

Louise

[ollypenrice]

You say you want a scope matched to a DSLR. If, by this, you mean you want to do long exposure deep sky imaging rather than video capture planetary imaging then you need to play to the camera's specification. It will be best suited to a fast focal ratio and a short focal length.  The pixels are really too small for long focal lengths in deep sky work.

You might learn a lot by reading Steve Richards' Making Every Photon Count. Many equipment choices are very counter intuitive in this game.

Olly

[newbie alert]

Yes i have a 8 inch sct and a designated planetry camera for planets and have been using it with a focal reducer for some deep sky targets.. some of my future targets are far too big to use my sct as its got a narrow field of view..looking for something wider field but dont understand if say a apo is better than a triplet etc as dont understand the terminolgy..

i should of said id be using a dslr rather than a ccd

[ollypenrice]

Some definitions: an apochromatic scope is simply one which brings all the colours to almost the same point of focus. This means a star will be a tight little circle of light. If the scope is not apochromatic then there will be a central star but some colours, notably blue, will be out of focus and make a spreading or bloated glow around the star.

Doublets are refractors with two front lenses. Triplets have three. There are also quadruplets with four and other designs with five lenses. A good doublet will be closer to apochromatic than a bad triplet but a good triplet will always be more apochromatic than a good doublet.

Large chips need a flat field so a rear lens element is essential. This can be built into quadruplet and five element designs but doublets and triplets will need an add-on flattener at the rear.

Olly

[newbie alert]

Thanks Olly,thats the kind of answer i was looking for..thanks very much..

[PeterCPC]

Short focal length for DSOs and as long a focal length as you can manage for Planetary. My C9.25 is great for planetary.

Peter

 

[Astrofriend]

If you find it interesting to read you can follow my way to build an astrophotosystem here:

http://astrofriend.eu/astronomy/projects/project-mechanical-construction-adapters-for-apo-refractor/project-mechanical-construction-adapters-for-apo-refractor.html

 

A good focuscontrol is important:

http://astrofriend.eu/astronomy/projects/project-motor-focus/project-motor-focus.html

 

And dewshield is also important:

http://astrofriend.eu/astronomy/projects/project-heating-band/project-heating-band.html

 

I will say that some part is difficult to built and find right parts, here I have collect a lot of useful links:

http://astrofriend.eu/links/links.html#astronomy

 

Merry Christmas!

 

/Lars

 

 

[Starwiz]

On 12/23/2016 at 22:19, Astrofriend said:

If you find it interesting to read you can follow my way to build an astrophotosystem here:

http://astrofriend.eu/astronomy/projects/project-mechanical-construction-adapters-for-apo-refractor/project-mechanical-construction-adapters-for-apo-refractor.html

 

A good focuscontrol is important:

http://astrofriend.eu/astronomy/projects/project-motor-focus/project-motor-focus.html

 

And dewshield is also important:

http://astrofriend.eu/astronomy/projects/project-heating-band/project-heating-band.html

 

I will say that some part is difficult to built and find right parts, here I have collect a lot of useful links:

http://astrofriend.eu/links/links.html#astronomy

 

Merry Christmas!

 

/Lars

 

 

Wow! That's a very comprehensive description and quite interesting.  Thanks for sharing.

John

[iapa]

On 07/12/2016 at 11:08, PeterCPC said:

Short focal length for DSOs and as long a focal length as you can manage for Planetary. My C9.25 is great for planetary.

Peter

 

Where does short focal length stop and long start?

Long focal length; 1500mm and above?

Short<1000? <600? 400?

I've still not got my head in that space yet.

[PeterCPC]

I would say that short focal length is up to about 650mm or so. Others may think otherwise. This would include the ED80 and 130pds etc. I would count your 8"sct as long focal length.

Peter

[iapa]

1 minute ago, PeterCPC said:

I would say that short focal length is up to about 650mm or so. Others may think otherwise. This would include the ED80 and 130pds etc. I would count your 8"sct as long focal length.

Peter

While both 8" reflector with 0.9 coma corrector and 8" SCT with 0.63 reducer/flattener sit at the firmly in the middle? at 1000mm +/- 100 or are we still high end of short focal length

Such a subjective hobby for something that requires high degrees of precision

 

[PeterCPC]

As you say it is subjective but you want a low f number for DSO imaging but that is not an issue for planetary imaging. I have done planetary imaging at f50 for example.

Peter

[newbie alert]

Must have very dark skies and even better seeing conditions at f50..whats that a f10x 5 barlow?

[Alien 13]

Best imaging scope for a DSLR is a Samyang 135 mm F2 lens 

Alan

[Stub Mandrel]

130P-DS which is 580mm is good with a DSLR fro DSOs. I would consider my 150PL at 1200mm 'long' - that's what the 'L' stands for ;-) but i barlow it to about 2600 for planets.

[newbie alert]

Thanks for your replies..ive got it sorted in my head now

[ollypenrice]

For an imager it is really better to concentrate on pixel scale in arcsecs per pixel rather than focal length. This value depends on pixel size and focal length. FL is a kind of short cut in the discussion. There is a calculator on the FLO site and also one here: http://www.12dstring.me.uk/fov.htm

I would say that choosing a focal length giving between 2 and 3 arcseconds per pixel would give you a productive and enjoyable rig for starters. If you go below that (towards an arcsecond or so) you start to need very accurate autoguiding and you risk trying to resolve smaller details than the seeing and guiding will allow.

It is often said that anything below two arcseconds per pixel will give a coarse, blocky result but I don't find this to be so. These images were taken at 3.5"PP:

Olly