DSO Imaging on a budget

[ollypenrice]

On 24/12/2022 at 22:21, Ian McCallum said:

Some will claim an achromat for AP is sacrilege, but to some of us, it's all we can afford!😱

As Peter says, above, a Newtonian is an inexpensive choice and will trounce an achromatic refractor for imaging.

An achromat really is not a good option.

Olly

[MartinB]

But an achromatic is light and easy to mount.  They can work well through RGB and narrow band filters.  

[pipnina]

6 hours ago, ollypenrice said:

As Peter says, above, a Newtonian is an inexpensive choice and will trounce an achromatic refractor for imaging.

An achromat really is not a good option.

Olly

From my own experience, I can say that a 130-PDS (about as cheap as they come) is very good for the price. Once you learn how to handle collimation yourself it's pretty rock solid and trouble-free. Mine paired with the Baader MPCC did let some out-of-frame reflections through but for 350 for scope and corrector you can't complain.

I did find that it wasn't very suitable for a mono setup though, as the focuser is weak and the cost of upgrading it didn't make sense for the scope. All-in-all it is a strong recommend for someone on a tight budget!

I will say though that for some reason, even the step up to an 8" newt is probably a bad move on a budget. For some reason even though it doesn't sound a lot on paper, that weight and size creates a huge amount of flex. My TS PHOTON 8" F4 was a nightmare that I eventually ran from light-speed. I guess that larger than 6" newts are best left to more expensive, higher-quality models...

My 2p anyway. Adding this for any newbies reading the thread.

[vlaiv]

What sort of budget are we talking about?

How about this little fella?

https://www.teleskop-express.de/shop/product_info.php/info/p14791_Tecnosky-AC-62-520-refractor---optical-tube.html

No need for flatteners / correctors and I think that it has CA well controlled (I used to get virtually CA free images from similar setup - 66 mm aperture 500mm FL with the use of Wratten #8 filter - and that is plain doublet not a Petzval).

 

[bosun21]

1 hour ago, vlaiv said:

What sort of budget are we talking about?

How about this little fella?

https://www.teleskop-express.de/shop/product_info.php/info/p14791_Tecnosky-AC-62-520-refractor---optical-tube.html

No need for flatteners / correctors and I think that it has CA well controlled (I used to get virtually CA free images from similar setup - 66 mm aperture 500mm FL with the use of Wratten #8 filter - and that is plain doublet not a Petzval).

 

Wow! 5.5kg for a 62mm frac. But definitely worth considering.

[vlaiv]

2 minutes ago, bosun21 said:

Wow! 5.5kg for a 62mm frac. But definitely worth considering.

I think that 5.5Kg is whole package, including all accessories and case.

TS has exactly the same scope, minus some accessories in its lineup at considerably higher price (makes perfect sense - amici prism, T2 extension and two eyepieces cost about -70euro, right? )

https://www.teleskop-express.de/shop/product_info.php/info/p14747_TS-Optics-62-mm-f-8-4-4-Element-Flatfield-Refractor-for-Observation-and-Photography.html

there in stats it says that telescope itself is about 1Kg

[bosun21]

17 minutes ago, vlaiv said:

I think that 5.5Kg is whole package, including all accessories and case.

TS has exactly the same scope, minus some accessories in its lineup at considerably higher price (makes perfect sense - amici prism, T2 extension and two eyepieces cost about -70euro, right? )

https://www.teleskop-express.de/shop/product_info.php/info/p14747_TS-Optics-62-mm-f-8-4-4-Element-Flatfield-Refractor-for-Observation-and-Photography.html

there in stats it says that telescope itself is about 1Kg

Thanks , that’s makes a lot more sense. It’s definitely an interesting little scope.

[Ian McCallum]

8 hours ago, ollypenrice said:

As Peter says, above, a Newtonian is an inexpensive choice and will trounce an achromatic refractor for imaging.

An achromat really is not a good option.

Olly

But I love the challenge...🤪🤣

[bosun21]

22 minutes ago, vlaiv said:

I think that 5.5Kg is whole package, including all accessories and case.

TS has exactly the same scope, minus some accessories in its lineup at considerably higher price (makes perfect sense - amici prism, T2 extension and two eyepieces cost about -70euro, right? )

https://www.teleskop-express.de/shop/product_info.php/info/p14747_TS-Optics-62-mm-f-8-4-4-Element-Flatfield-Refractor-for-Observation-and-Photography.html

there in stats it says that telescope itself is about 1Kg

They have some discrepancies 

[Ian McCallum]

1 hour ago, pipnina said:

From my own experience, I can say that a 130-PDS (about as cheap as they come) is very good for the price. Once you learn how to handle collimation yourself it's pretty rock solid and trouble-free. Mine paired with the Baader MPCC did let some out-of-frame reflections through but for 350 for scope and corrector you can't complain.

I did find that it wasn't very suitable for a mono setup though, as the focuser is weak and the cost of upgrading it didn't make sense for the scope. All-in-all it is a strong recommend for someone on a tight budget!

I will say though that for some reason, even the step up to an 8" newt is probably a bad move on a budget. For some reason even though it doesn't sound a lot on paper, that weight and size creates a huge amount of flex. My TS PHOTON 8" F4 was a nightmare that I eventually ran from light-speed. I guess that larger than 6" newts are best left to more expensive, higher-quality models...

My 2p anyway. Adding this for any newbies reading the thread.

I've already got an 8" Newt, but not exactly EQ mount friendly!🙄🤣

[vlaiv]

1 minute ago, bosun21 said:

They have some discrepancies 

I think it is more down to people entering data on their website than anything else. There is really only one model of that scope and it has been around for quite some time:

https://www.skyatnightmagazine.com/reviews/telescopes/orion-starblast-62mm-compact-travel-refractor/

(review from 2015)

[vlaiv]

If we really want to go budget friendly on newtonian - we should be looking for 1.25" sized coma corrector. There are few very affordable scopes that are 4-5" class.

I don't mind 130PDS - I just wonder once you add 2" CC is it still a budget option?

[pipnina]

54 minutes ago, vlaiv said:

If we really want to go budget friendly on newtonian - we should be looking for 1.25" sized coma corrector. There are few very affordable scopes that are 4-5" class.

I don't mind 130PDS - I just wonder once you add 2" CC is it still a budget option?

Compared to other AP scopes, I think the 300 I spent on my 130PDS + Baader MPCC was pretty budget! The mount (HEQ5) cost more than twice as much in 2017 prices, and I don't think the HEQ5 can handle too much more than the 650mm fl / 1.28" pixels that scope gave me with my DSLR.

I think it's a bit pricier today, but I'd still struggle to find a scope + corrector that beats it on a value perspective! A 1.25" corrector will probably be sub-optimal for a lot of beginner / budget minded people- a lot of them will use APS-C or 4/3 DSLRs or mirrorless cameras that they may already own or buy second hand off ebay.

[ONIKKINEN]

I think i would rather have coma that can be fixed later by saving money for a coma corrector than have an achromat that will always have CA. Fringe killer/wratten#8 will hide it, but there is no way to get rid of it fully without a compromise. We are also comparing a tiny 62mm aperture to 130mm aperture so i think the choice is quite clear.

My vote for the ultimate budget DSO telescope setup would be an EQ5, with DIY onstep motors if necessary, and a 130PDS. If the imager chooses a dedicated astro cam instead of a second hand DSLR the sensor size will be quite small in budget models so coma will be less of a nuisance than with a large sensor. Second hand DSLRs are often the cheapest so probably not the case.

Something that is easy to overlook when figuring out a budget build is that you really cant afford to buy cheap/what you dont want as in the long run the intermediate choices cost you money instead of saved it. You should budget the kit so that there are the least amount of compromises or things you have to completely replace in a few years or however long it takes for you to save money for it. If you buy the achromat but you want to replace it later because of the CA and the small aperture you are now in the negative budget wise for however much the scope cost. Maybe you can sell it and get 70% back, but that is still a loss and no guarantee you can get rid of it in a timely manner. So my advice is to look ahead for something you want rather than something you think you could get away with in a pinch. Of course it doesnt mean that you must save up for a Planewave CDK, but you get the idea - think 2 steps ahead when budgeting.

[ollypenrice]

1 hour ago, Ian McCallum said:

But I love the challenge...🤪🤣

God knows, we all love the challenge! 🤣 Good for you.

Olly

[Ratlet]

Depends on the focal length.  Takumar 200mm is about £40-60 with a 200mm focal length.  Still testing the Tair and haven't made my mind up but 300mm at £60-100.

As to the coma correctors, you could always just crop the image.  It is photography and part of it is framing the image.

Honestly when I, on a whim, tried my 130pds which I use for visual with my Hypercam 533c which has a 1" sensor.  I looked at the stars in the corners and then looked at the (many, MANY) posts concerning coma correctors and back spacing and tilt and thought. "Nah, this will do"

It depends on what you want from it I guess.  I mostly just want to share space images on FB and get a smiley face and like from me mum so I've got a fairly low bar lol.

[ollypenrice]

2 minutes ago, Ratlet said:

Depends on the focal length.  Takumar 200mm is about £40-60 with a 200mm focal length.  Still testing the Tair and haven't made my mind up but 300mm at £60-100.

As to the coma correctors, you could always just crop the image.  It is photography and part of it is framing the image.

Honestly when I, on a whim, tried my 130pds which I use for visual with my Hypercam 533c which has a 1" sensor.  I looked at the stars in the corners and then looked at the (many, MANY) posts concerning coma correctors and back spacing and tilt and thought. "Nah, this will do"

It depends on what you want from it I guess.  I mostly just want to share space images on FB and get a smiley face and like from me mum so I've got a fairly low bar lol.

Sound!

Olly

[vlaiv]

Ok, I'm going to put a spin on this.

How about 4" scope that does not need a corrector, works with up to APS-C size sensor, weighs less than 2Kg, costs £205 and no one "in their right mind" would recommend as an imaging scope?

(need I mention that I'm quite happy not to be in my right mind and say that this will actually work if one treats it in particular way).

 

[ONIKKINEN]

1 minute ago, vlaiv said:

Ok, I'm going to put a spin on this.

How about 4" scope that does not need a corrector, works with up to APS-C size sensor, weighs less than 2Kg, costs £205 and no one "in their right mind" would recommend as an imaging scope?

(need I mention that I'm quite happy not to be in my right mind and say that this will actually work if one treats it in particular way).

 

Does this scope exist? Seems too good to be true. Long focus achromat maybe but the 2kg is suspect?

[vlaiv]

1 minute ago, ONIKKINEN said:

Does this scope exist? Seems too good to be true. Long focus achromat maybe but the 2kg is suspect?

https://www.firstlightoptics.com/maksutov/skywatcher-skymax-102-ota.html

 

[ONIKKINEN]

2 minutes ago, vlaiv said:

https://www.firstlightoptics.com/maksutov/skywatcher-skymax-102-ota.html

 

Now this is a challenge! Never even considered maksutovs but actually why not? Exposure times will be inconvenient but a beginner has 10 other things to worry about so they probably dont care.

[vlaiv]

1 minute ago, ONIKKINEN said:

Now this is a challenge! Never even considered maksutovs but actually why not? Exposure times will be inconvenient but a beginner has 10 other things to worry about so they probably dont care.

Bin data x3 and you are effectively working with 100mm / 433.33mm scope.

Yes, three things will be drawback to using it:

1. read noise. it will take quite a bit of exposure to swamp read noise, but it might be viable option in LP conditions where one does not need to expose for long to swamp read noise with LP

2. FOV - of course, FOV will be much smaller, but not that small:

quite usable on some of larger galaxies and nebulae. Old favorite - M42 would need a mosaic:

but that is also true for someone purchasing dedicated camera like ASI585 and using it with 130PDS:

3. Moving mirror - which probably means using OAG to guide rather than guide scope, but OAGs can actually be cheaper than some guide scopes, so they should be considered a budget option

 

[ollypenrice]

41 minutes ago, ONIKKINEN said:

Does this scope exist? Seems too good to be true. Long focus achromat maybe but the 2kg is suspect?

How did I guess that some serious binning was at the back of Vlaiv's mind????  But he might have a point.

Olly

[ONIKKINEN]

31 minutes ago, vlaiv said:

Bin data x3 and you are effectively working with 100mm / 433.33mm scope.

Yes, three things will be drawback to using it:

1. read noise. it will take quite a bit of exposure to swamp read noise, but it might be viable option in LP conditions where one does not need to expose for long to swamp read noise with LP

2. FOV - of course, FOV will be much smaller, but not that small:

quite usable on some of larger galaxies and nebulae. Old favorite - M42 would need a mosaic:

but that is also true for someone purchasing dedicated camera like ASI585 and using it with 130PDS:

3. Moving mirror - which probably means using OAG to guide rather than guide scope, but OAGs can actually be cheaper than some guide scopes, so they should be considered a budget option

 

Since you mentioned M81 here i might mention that it was one of the first targets i tried with a 200mm newtonian on an EQM35 unguided. Didnt produce a great image but not because of the lack in guiding. This high in declination the sky moves so slowly that the beginner might forego guiding completely.

The mosaicing thing could be trouble, i think you need to have more or less perfect flats to give yourself a chance of getting a seamless mosaic and the budget mak might not be up to that with its movable mirror and maybe not as sturdy a visual back as it should be (not sure about that but would imagine its not rock solid).

[vlaiv]

10 minutes ago, ONIKKINEN said:

The mosaicing thing could be trouble, i think you need to have more or less perfect flats to give yourself a chance of getting a seamless mosaic and the budget mak might not be up to that with its movable mirror and maybe not as sturdy a visual back as it should be (not sure about that but would imagine its not rock solid).

You are probably right. Using DSLR body on such scope is probably not recommended - but why not use mirrorless camera?

In fact - we might be expecting too much of a beginner. Perfect flats for mosaic?

Yep, that is no flats mosaic on ST102 (notice lack of chromatic aberration, who said fast achromats can't be used for OSC imaging?) taken from Bortle 7-8 skies with ASI185 - uncooled.

I think that while image is not perfect, many beginners would be satisfied with such result?.