SW 200, 150 or 130PDS

[bottletopburly]

Wise words ?

[stuplu82]

This may seem like a very basic question to you guys, but if i use a T-ring adaptor for my DSLR and scope, how do you also attach a coma corrector or field flattener?

Does the CC or FF replace the t-Ring adaptor and attach to the camera?

Also, if i buy the 0.9x SW CC, it says it also requires 55mm back focus. Is this only for CCD camera's and the Nikon camera will take care of this itself?

[vlaiv]

1 minute ago, stuplu82 said:

This may seem like a very basic question to you guys, but if i use a T-ring adaptor for my DSLR and scope, how do you also attach a coma corrector or field flattener?

CC usually comes with one of two threads for attachments - either M48 (which is 2" filter thread) or T2 thread. It usually also has M48 thread on telescope side.

Putting all together would be like this:

CC - (M48/T2 adapter) - T2 adapter for DSLR - DSLR body

M48/T2 adapter is needed if particular CC has M48 thread on camera side. If it already has T2, then you don't need it.

You might need certain distancing rings to get optimum distance for CC. You put everything in 2" focuser and you are set to go.

For example, Baader RCC1 has both T2 and M48 threads on camera side - so you can use either. It also need:s 91.5mm from T2 and 94.5mm from M48 thread as working distance so you will need some spacers / distancing rings.

Baader MPCC on the other hand has T2 (M42x0,75) and M48x0,75 (male) and shorter working distance of 55mm from the T2 thread and 58mm from the M48 thread

First thing to do would be to decide on which Coma Corrector you will be getting and then check the specs for that CC and see what sort of adapters / extensions you will need.

Canon DSLR + T2 adapter should provide 55mm of optical path, and you will find that most CCs have that exact working distance.

[stuplu82]

3 minutes ago, vlaiv said:

CC usually comes with one of two threads for attachments - either M48 (which is 2" filter thread) or T2 thread. It usually also has M48 thread on telescope side.

Putting all together would be like this:

CC - (M48/T2 adapter) - T2 adapter for DSLR - DSLR body

M48/T2 adapter is needed if particular CC has M48 thread on camera side. If it already has T2, then you don't need it.

You might need certain distancing rings to get optimum distance for CC. You put everything in 2" focuser and you are set to go.

For example, Baader RCC1 has both T2 and M48 threads on camera side - so you can use either. It also need:s 91.5mm from T2 and 94.5mm from M48 thread as working distance so you will need some spacers / distancing rings.

Baader MPCC on the other hand has T2 (M42x0,75) and M48x0,75 (male) and shorter working distance of 55mm from the T2 thread and 58mm from the M48 thread

First thing to do would be to decide on which Coma Corrector you will be getting and then check the specs for that CC and see what sort of adapters / extensions you will need.

Canon DSLR + T2 adapter should provide 55mm of optical path, and you will find that most CCs have that exact working distance.

 

Thanks for in depth reply

Im looking to buy the 0.9x SW CC with adapters, but it says it also requires 55mm back focus in the description. Is this only for CCD camera's and the Nikon camera will take care of this itself? or do i still need distancing rings?

 

https://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html#about_this_product

 

[Stub Mandrel]

130P-DS does work fine on EQ3, guiding is almost as good as HEQ5.

BUT... I 'upgraded' to an HEQ5 and though the impact on guiding has been modest the ease of setting up is well worth it.

I just wish I had the patience to set up both mounts and use the EQ3 with an unguided camera lens combination.

[vlaiv]

Just now, stuplu82 said:

 

Thanks for in depth reply

Im looking to buy the 0.9x SW CC, but it says it also requires 55mm back focus in the description. Is this only for CCD camera's and the Nikon camera will take care of this itself? or do i still need distancing rings?

This means that distance between thread on 0.9x SW CC to sensor needs to be 55mm - what ever sensor you use.

It is most likely that Nikon camera and matching T2 ring will add up to exactly 55mm - but it would be best to check it out.

Here is information that will help:

https://en.wikipedia.org/wiki/Flange_focal_distance

This is distance calculated for lens. Since your T2 ring will be put instead of lens, you need to add optical length of matching T2 ring and flange focal distance of your camera. Note that T-mount (T2) has flange focal distance of 55mm, this means that with T2 ring for your camera - you should be able to use any T/T2 mount lens as it would need 55mm same as CC.

Let's take Nikon-F mount (I'm just guessing here - but principle is the same) - it has 46.50mm flange distance.

If you get this adapter for example:

https://www.teleskop-express.de/shop/product_info.php/info/p10581_TS-Optics-ultrashort-Adapter-from-T2--M42x0-75--to-NIKON-DSLR-Bayonet.html

which has 1mm of optical path - you will need additional 7.5mm extension. Mind you above item is meant as "Ideal for applications with short backfocus" (description on the page), so it's not standard T2 ring.

I'm trying to find regular one with description, to show you that they have 8.5mm optical path, but nobody seems to list optical length of standard Nikon T2 adapters. But it should be as T2 standard - 55mm.

[Stub Mandrel]

21 minutes ago, stuplu82 said:

Im looking to buy the 0.9x SW CC with adapters, but it says it also requires 55mm back focus in the description. Is this only for CCD camera's and the Nikon camera will take care of this itself? or do i still need distancing rings?

55mm is the standrd flange distance for all T-mount lenses, so fitting any standard T-mount to DSLR adaptor to the CC will automatically give you 55mm back focus. With non-DSLRs you will need an adaptor that gives you (55mm-camera flange distance) spacing.

[glowingturnip]

I think you're arriving at a decent decision for 150PDS + HEQ5.  I've got a 200 but it is a lump and needs a stronger mount, but I do like the zoom it gives me - I like my nebulae in my face, not lost in a star field.  The 150 sounds like decent middle ground if you've already used a 130 and want to go longer.

You'll need a coma corrector, as above, and you should spend some time in the field experimenting with different spacings to get it right, mine ended up needing a whole 1mm longer than the default.

You'll also need to be on top of your collimating, I would suggest getting both a Cheshire and a laser collimator and spending the time learning how to nail it.  My 200PDS was quite far off-collimated when I got it.

Also check for light spill round the bottom of the tube, try taking a quick picture with a light shining at the bottom end, see if you get any light spill on the photo - I bought some blackout blind material and a bungee cord to fix mine

[Adam J]

4 hours ago, Stub Mandrel said:

130P-DS does work fine on EQ3, guiding is almost as good as HEQ5.

BUT... I 'upgraded' to an HEQ5 and though the impact on guiding has been modest the ease of setting up is well worth it.

I just wish I had the patience to set up both mounts and use the EQ3 with an unguided camera lens combination.

I get an RMS error of about 0.8 arc-seconds on my HEQ5 pro with the 130PDS on it measured over a 5min exposure....I struggle to believe that you are getting 0.8 arc-seconds / pixel RMS from a EQ3. 

[Stub Mandrel]

45 minutes ago, Adam J said:

I get an RMS error of about 0.8 arc-seconds on my HEQ5 pro with the 130PDS on it measured over a 5min exposure....I struggle to believe that you are getting 0.8 arc-seconds / pixel RMS from a EQ3. 

Guide graph with EQ3:

See these threads. I used to get about 1.30" most nights and sometimes 0.80" with the EQ3. I've been frustrated not to get any better with the HEQ5:

 

[Whistlin Bob]

Lots of good advice on here. You probably already have information overload, but my thoughts:

- I bought an HEQ5 second hand, it's been great and I've almost never heard a bad word said about them, except for the polar alignment bolts which are a bit rubbish but can be replaced.

- My 200p works fine on the mount but is big and unwieldy to work with.

- I use the SW CC and adaptor on a Canon DSLR and it's been painless and effective.

- I doubt you'll regret either 130 or 150, but aperture is much less important than f-ratio for ap. The main difference is in field of view- think about what you want to image and use this to check what you'll get on your camera. For example- the 150 will struggle to fit in Andromeda on an APS-C sensor, but a 130 will be fine. On the other hand smaller objects are tiny on it.

https://astronomy.tools/calculators/field_of_view/ 

Good luck and don't worry too much- all of the choices you're juggling with are good ones.

[stuplu82]

16 hours ago, Whistlin Bob said:

Lots of good advice on here. You probably already have information overload, but my thoughts:

- I bought an HEQ5 second hand, it's been great and I've almost never heard a bad word said about them, except for the polar alignment bolts which are a bit rubbish but can be replaced.

- My 200p works fine on the mount but is big and unwieldy to work with.

- I use the SW CC and adaptor on a Canon DSLR and it's been painless and effective.

- I doubt you'll regret either 130 or 150, but aperture is much less important than f-ratio for ap. The main difference is in field of view- think about what you want to image and use this to check what you'll get on your camera. For example- the 150 will struggle to fit in Andromeda on an APS-C sensor, but a 130 will be fine. On the other hand smaller objects are tiny on it.

https://astronomy.tools/calculators/field_of_view/ 

Good luck and don't worry too much- all of the choices you're juggling with are good ones.

I want to DSO rather than planetary/moon AP. If and when i want to move into that area, i will likely buy a refactor and try my hand at AP with it. 

The good news it that there doesn't seem to be any bad words against the 130 or 150. I did check the FoV of the 150 and yes, M31 wont fit into it, but I think im okay with that. 

Out of curiosity, has anyone used the 130/150 for planetary AP? Do you recommend using a barlow at all? 

[Stub Mandrel]

1 hour ago, stuplu82 said:

Out of curiosity, has anyone used the 130/150 for planetary AP? Do you recommend using a barlow at all? 

Yes and yes.

My 1509PL at 1200mm is a far better choice for planetary, and I use that with an x3 barlow.

[FaDG]

2 hours ago, stuplu82 said:

Out of curiosity, has anyone used the 130/150 for planetary AP? Do you recommend using a barlow at all? 

Yes, definitely, although my main interest is DSO too, there are times when seeing is great and a Planet particularly well placed. 

Here you have a jupiter and a Mars taken with the 150pds, ASI120 and a 2x barlow used at 2,6 with appropriate spacing. 

For this the 150 is better than the 130, but the 200 is better still. So, make your choice based on your primary interest, and complement as you want for moon and planetary! 

 

 

 

[Adam J]

21 hours ago, Stub Mandrel said:

I used to get about 1.30" most nights and sometimes 0.80" with the EQ3. I've been frustrated not to get any better with the HEQ5

You say sometimes 0.8 with a EQ3.

I get 0.8 reliably with a HEQ5 pro, but I can get 0.6 sometimes. 

[Stub Mandrel]

44 minutes ago, Adam J said:

You say sometimes 0.8 with a EQ3.

I get 0.8 reliably with a HEQ5 pro, but I can get 0.6 sometimes. 

Ditto. There's no doubt it's easier to get good results with the HEQ5 - that's why I got one.

I only said "130P-DS does work fine on EQ3, guiding is almost as good as HEQ5. "

With my 450D the 130PDS and CC comes out at 3.66" per pixel. The difference in guide quality between my EQ3 and my HEQ5 is academic.

For the 150PL at 0.89" per pixel the HEQ5 is clearly a better choice.

[dannybgoode]

5 hours ago, stuplu82 said:

I want to DSO rather than planetary/moon AP. If and when i want to move into that area, i will likely buy a refactor and try my hand at AP with it. 

Lots of people image DSO’s on short FL fracs. Don’t forget you want the camera to match the scope so it does not under or over sample too much. 

And , as you have discovered there’s a good number of DSO’s that are really quite large. 

Finally one thing I’ve been getting my head around with astronomy is not whether an object is larger or smaller at certain magnifications but rather the field of view is wider or narrower. 

All that said you know my thoughts on the 150. Hasn’t stopped my buying a nice frac as well though

[glowingturnip]

fwiw, planetary with the 200pds, with, ahem, one barlow in the back of another, qhy5liic