Imaging with the 130pds

[Adam J]

M101, 50 x 5mins ISO800, Over Two Nights, 130PDS, HEQ5pro, Orion + QHY5L II Mini Guider, Astronomik CLS Filter.

Having trouble with color balance, let me know what you think guys

I may add some longer exposures next to bring out the fainter trails of the spiral arms more and then combine them with this image.

 

 

 

Edited March 26, 2017 by Adam J

[dyfiastro]

Hi everyone.

Managed to get out for a brief period the other night.
Grabbed a quick 4 panel lunar mosaic and my first attempt of the year at Jupiter.
Conditions and seeing took a nose dive after the mosaic but pretty happy with the result

4 Panel Mosaic - ASI120MC-S (No Barlow)

Jupiter - ASI120MC-S (2x + 3x Barlow Stacked)

 

[rotatux]

Nice moon sharpness, but the green tint on highlights give it much of... an alien look

In Jupiter it was just in time to catch the shadow on the disk's edge, congratulations.

[rml63]

Your moon shot is my new favourite, Well Done.

 

Mike

[mak90fan]

Yes, my fave moon shot of all time, you should market that photo, well done!!

[mAnKiNd]

Greetings everyone from sunny Cyprus and Happy Easter to you all. This is my first post on this great forum.

I ordered a 130PDS plus SW 0.9x Coma Corrector from my local astronomy shop and it should arrive in the next 2-3 weeks. 

However, having read through the entirety of this monumental thread, I’ve come to the conclusion that the SW CC is not my best choice.

Since it’s Easter time, I have a few days until Wednesday when the shops reopen to alter my order. The shop manager is being very helpful and is willing to amend my order accordingly.

I’m writing to you seeking advice for which coma corrector is the best for image quality, based on users' experience. I’ve gathered the following information from this great thread, the links within it and also from a wider google search.

1)    Skywatcher 0.9x CC, 2-element – Pros: reduced focal length for easier guiding and wider field of view. Cons: Internal reflections on bright stars. Chromatic aberrations on mid-sized stars. A focus point which causes a protruding drawtube “chopping” off stars, necessitating the need to either shave the drawtube, move the mirror up, or both. I appreciate the mods made by Uranium to the SW CC, but I’m not looking forward to so much DIY.

2)    Baader MPCC MKIII, 2- element - Pros: less to no internal reflections. No change in focal length. Cons: demanding accuracy for correct spacing. Chromatic aberration on mid sized stars. Bloating of stars across the field. Same protrusion in drawtube as above.

3)    TS/GSO coma corrector, 4-element – Pros: no internal reflections. No chromatic aberrations. No star bloating. No focuser protrusion. Cons: 14% increase in focal length making guiding slightly harder and also gives a reduced field of view.

Please do correct me if I’m incorrect regarding any of the above points. 

If not, then it seems to me that the TS/GSO is the best option with regards to image quality - no need to change primary position or shave the drawtube and you get a higher quality image with regards to no reflections and no chromatic aberrations. I can deal with the increase in FL/FR and reduction in FOV, no worries. I have another scope for that with a superb FOV.

My local shop is happy to order me the GSO CC instead of the SW.

If possible, could the above be confirmed by any of you to reassure me of my assessment?

I know that Louise has posted often about both the Baader and the GSO, but her comments regarding image quality pertain more so to the Baader. In general, there seems to be much more information on the performance of the SW and Baader, so I’m looking for more info regarding the TS/GSO if possible.

Many thanks to all you wonderful people sharing your wonderful experiences of the cosmos in our night sky.

Looking forward to your replies.
Sincerely,
Minos.
 

Edited April 16, 2017 by mAnKiNd
Clarity and forgot a missing info.

[wimvb]

Welcome to sgl.

Fyi, I use the baader cc with my 150pds, and it works great. Together with my pentax dslr, I didn't need any spacers. But the pentax has a little more 'back focus' than a canon.

I wouldn't worry about guiding issues for any of the CCs, at the native fl of the scope it's quite easy to guide.

[Thalestris24]

2 hours ago, mAnKiNd said:

Greetings everyone from sunny Cyprus and Happy Easter to you all. This is my first post on this great forum.

I ordered a 130PDS plus SW 0.9x Coma Corrector from my local astronomy shop and it should arrive in the next 2-3 weeks. 

However, having read through the entirety of this monumental thread, I’ve come to the conclusion that the SW CC is not my best choice.

Since it’s Easter time, I have a few days until Wednesday when the shops reopen to alter my order. The shop manager is being very helpful and is willing to amend my order accordingly.

I’m writing to you seeking advice for which coma corrector is the best for image quality, based on users' experience. I’ve gathered the following information from this great thread, the links within it and also from a wider google search.

1)    Skywatcher 0.9x CC, 2-element – Pros: reduced focal length for easier guiding and wider field of view. Cons: Internal reflections on bright stars. Chromatic aberrations on mid-sized stars. A focus point which causes a protruding drawtube “chopping” off stars, necessitating the need to either shave the drawtube, move the mirror up, or both. I appreciate the mods made by Uranium to the SW CC, but I’m not looking forward to so much DIY.

2)    Baader MPCC MKIII, 2- element - Pros: less to no internal reflections. No change in focal length. Cons: demanding accuracy for correct spacing. Chromatic aberration on mid sized stars. Bloating of stars across the field. Same protrusion in drawtube as above.

3)    TS/GSO coma corrector, 4-element – Pros: no internal reflections. No chromatic aberrations. No star bloating. No focuser protrusion. Cons: 14% increase in focal length making guiding slightly harder and also gives a reduced field of view.

Please do correct me if I’m incorrect regarding any of the above points. 

If not, then it seems to me that the TS/GSO is the best option with regards to image quality - no need to change primary position or shave the drawtube and you get a higher quality image with regards to no reflections and no chromatic aberrations. I can deal with the increase in FL/FR and reduction in FOV, no worries. I have another scope for that with a superb FOV.

My local shop is happy to order me the GSO CC instead of the SW.

If possible, could the above be confirmed by any of you to reassure me of my assessment?

I know that Louise has posted often about both the Baader and the GSO, but her comments regarding image quality pertain more so to the Baader. In general, there seems to be much more information on the performance of the SW and Baader, so I’m looking for more info regarding the TS/GSO if possible.

Many thanks to all you wonderful people sharing your wonderful experiences of the cosmos in our night sky.

Looking forward to your replies.
Sincerely,
Minos.
 

Hi

Thanks for quoting me! Yes, the gso increases focal length slightly but doesn't have a negative effect on image quality or on guiding. 

Louise

[Guest Tuomo]

Anyone happen to have link for that TS/GSO CC? Im about to buy 130pds too and I really find spacing with Baader CC confusing...

[alacant]

15 minutes ago, Tuomo said:

TS/GSO CC

You can see it here. The main problem is the amount of front focus it needs. It's right on the limit of my reflector. Even if it will reach focus, I wouldn't like to guess if the pds focuser will hold a dslr satisfactorily at that distance. HTH.

[Guest Tuomo]

Owh...Thanks for the info.

 

[Thalestris24]

It's not a problem with the pds scopes as far as I recall (not used either of mine in ages).

Louise

[Guest Tuomo]

6 hours ago, Thalestris24 said:

It's not a problem with the pds scopes as far as I recall (not used either of mine in ages).

Louise

But you would recommend using Ts CC over Baader? TS is cheaper too....

[mAnKiNd]

13 hours ago, wimvb said:

Welcome to sgl.

Fyi, I use the baader cc with my 150pds, and it works great. Together with my pentax dslr, I didn't need any spacers. But the pentax has a little more 'back focus' than a canon.

I wouldn't worry about guiding issues for any of the CCs, at the native fl of the scope it's quite easy to guide.

Thank you for your input, yes I looked it up and the Pentax has 1.46mm extra flange focal distance than a Canon. May I ask, where would you say your focus point lies on the focuer, racked in, midway or racked out?

Thanks again.

12 hours ago, Thalestris24 said:

Hi

Thanks for quoting me! Yes, the gso increases focal length slightly but doesn't have a negative effect on image quality or on guiding. 

Louise

Thank you for all of your input Louise.

12 hours ago, alacant said:

You can see it here. The main problem is the amount of front focus it needs. It's right on the limit of my reflector. Even if it will reach focus, I wouldn't like to guess if the pds focuser will hold a dslr satisfactorily at that distance. HTH.

Hi Alacant, thank you for the photo, it is very useful to see the probable configuration with the TS/GSO CC and how far out the focuser is racked. If I may, you mention that you "wouldn't want to guess..", does that mean you haven't tried to image with this configuration to confirm that the PDS focuser wouldn't hold a DSLR properly without flexing? If this is the case, and it does indeed cause an issue with the GSO CC necessitating the focuser to be racked out all the way meaning it won't hold a DSLR properly, then i'll add it to my list of Cons I made for this CC. 

9 hours ago, Thalestris24 said:

It's not a problem with the pds scopes as far as I recall (not used either of mine in ages).

Louise

Thank you again Louise, it seems the PDS focuser would be able to hold then. If I remember correctly, and just to reiterate - you used your GSO CC with a filter wheel & DSLR, because the GSO CC gave you the nesccessary backfocus to enable this configuration - did you ever experience any flexing or other issues with that kind of load racked all the way out?


Thank you all again for your invaluable input.

[alacant]

32 minutes ago, mAnKiNd said:

meaning it won't hold a DSLR properly

I have a 150mm and even with a proper 2 1/2" r&p focuser it flexed, especially noticeable at low dec near the horizon where the turning force is radial rather than longitudinal. But Louise confirms it's ok with a pds so that should be fine. Stars are superior when compared with the Baader too, but it magnifies the image which IMHO defeats the object of having a wide field telescope. In the end, I sent back the TS, got a Baader, sent that back -something about the elements being the wrong way making the coma worse- and got a cheap cc from aliexpress; perfect!

[richyrich_one]

16 minutes ago, alacant said:

got a cheap cc from aliexpress; perfect!

I'd love to know which one you got in the end?

[Guest Tuomo]

1 minute ago, richyrich_one said:

I'd love to know which one you got in the end?

Me too!

[Stub Mandrel]

I have a Skywatcher CC, the only time I have had issues with bright star reflections so far was with Alnitak in frame, where I got a blue patch diametrically opposite the star.

It was fairly easy to remove (being in a relatively dark and empty bit of sky), so although it is a real effect, it isn't an overwhelming problem as few DSOs share a 130P-DS field of view with a star as bright as Alnitak (mag. 2).

As far as smaller stars are concerned I haven't noticed issues with CA or bloating, although i'm nor exactly at the cutting edge!

YMMV

[alacant]

1 hour ago, richyrich_one said:

which one you got in the end

Here it is. My telescope comet kit adaption connector eyepiece with 2".

[rotatux]

Hello mAnKiNd, welcome to SGL and wish you lucky weather with your new gear

19 hours ago, mAnKiNd said:

1)    Skywatcher 0.9x CC, 2-element [...] Cons: [...] Chromatic aberrations on mid-sized stars. [...]

Just like Neil, I have this CC and never saw any CA with whatever stars, apart from diffraction spikes of course :-P

19 hours ago, mAnKiNd said:

2)    Baader MPCC MKIII, 2- element [...] Cons: [...] Same protrusion in drawtube as above.

I don't have it but have seen how it's made and what others tell on it, and I'm pretty sure it does NOT have the protrusion problem of the SW.

The SW has it because it's collar prevents it from going deeper into the focuser. But the Baader can thread in as a M48 filter, allowing it to go I think at least 20mm deeper into the focuser, if you have the right 2"/T2 or EOS adapter.

[mAnKiNd]

2 hours ago, alacant said:

I have a 150mm and even with a proper 2 1/2" r&p focuser it flexed, especially noticeable at low dec near the horizon where the turning force is radial rather than longitudinal. But Louise confirms it's ok with a pds so that should be fine. Stars are superior when compared with the Baader too, but it magnifies the image which IMHO defeats the object of having a wide field telescope. In the end, I sent back the TS, got a Baader, sent that back -something about the elements being the wrong way making the coma worse- and got a cheap cc from aliexpress; perfect!

Dear alacant, thank you for your reply, your notes are appreciated. You confirm that in your hands, the GSO CC performed optically better than the baader CC. As for the large backfocus and flexing of the focuser, it seems as though the PDS may be sturdier. However, I would like further confirmation for this from users of the GSO CC, as your point is valid and any optical advantages from the GSO CC would be negated if there is significant flexing. 

2 hours ago, Stub Mandrel said:

I have a Skywatcher CC, the only time I have had issues with bright star reflections so far was with Alnitak in frame, where I got a blue patch diametrically opposite the star.

It was fairly easy to remove (being in a relatively dark and empty bit of sky), so although it is a real effect, it isn't an overwhelming problem as few DSOs share a 130P-DS field of view with a star as bright as Alnitak (mag. 2).

As far as smaller stars are concerned I haven't noticed issues with CA or bloating, although i'm nor exactly at the cutting edge!

YMMV

Dear Neil, thank you for your input and your notes on the infrequency in the appearance of the reflections with the SW CC. Although, when that is the case, it will be a nuisance to deal with to some degree. Good to know that you did not notice any CA or bloating. Having looked at pictures taken through the 130pds + SW CC, some of them do appear to me to indeed suffer from these artifacts, but then others do not, notably the images taken by Uranium. However, he reported to have undertaken significant work in order to get it to work at peak performance. Indeed, it seems that mileage does vary with this configuration. Thank you again for your reply.

14 minutes ago, alacant said:

Here it is. My telescope comet kit adaption connector eyepiece with 2".

Dear alacant, thank you for sharing a picture of your mystery CC, it has certainly added an extra dimension to the list of candidates. I do not mean to pry, but if you could possibly share any details on this item, it would be very informative for the rest of us, as you are in a more experienced position having tested three of these CC's. You ended your prior post with the word - "perfect", which sounds to me as if you've landed on the right CC for the 130PDS. Please advise if possible, many thanks again.

[mAnKiNd]

8 minutes ago, rotatux said:

Hello mAnKiNd, welcome to SGL and wish you lucky weather with your new gear

Just like Neil, I have this CC and never saw any CA with whatever stars, apart from diffraction spikes of course :-P

I don't have it but have seen how it's made and what others tell on it, and I'm pretty sure it does NOT have the protrusion problem of the SW.

The SW has it because it's collar prevents it from going deeper into the focuser. But the Baader can thread in as a M48 filter, allowing it to go I think at least 20mm deeper into the focuser, if you have the right 2"/T2 or EOS adapter.

Dear Fabien, thank you for your reply and your wishes  Great to hear from another user of the SW CC that there is no CA. It seems as though modifications, whether to the drawtube, primary mirror position, or the collar of this CC are still necessary though to deal with the protrusion caused by this configuration. Also great to hear that the the protrusion is avoided with the baader CC. I have the Baader EOS locking ring. Thank you for taking the time to share your notes, much appreciated.

Edited April 17, 2017 by mAnKiNd

[Stub Mandrel]

30 minutes ago, alacant said:

Here it is. My telescope comet kit adaption connector eyepiece with 2".

Looks suspiciously "similar " to my slightly battlescarred Skwatcher one...

Time to clean that filter...

 

[wimvb]

@mAnKiNd:

Here's a pic with the focus settings of my scope/cc/camera.

The line marked K20D is for just the camera. The line below is for camera with Baader CC.

[mAnKiNd]

1 minute ago, wimvb said:

@mAnKiNd:

Here's a pic with the focus settings of my scope/cc/camera.

The line marked K20D is for just the camera. The line below is for camera with Baader CC.

Dear Wim, thank you for sharing this picture, very informative indeed, much appreciated!