ASI1600 + EFW coma corrector extender / spacer problem

[Tommohawk]

Funny thing - I have an ASI1600 + EFW and am connecting to SW coma corrector which requires 55mm spacing. The camera is 6.5mm the EFW is 20mm, total 26.5, so 28.5mm spacer required - sound correct hopefully?

But the suppllied spacers are 21mm and 16.5mm which doesnt help (and doesnt seem correct even for a colour ASI1600 with no EFW) There is also a 11mm female/female adapter and a very short 1.5mm male/male adapter, so I guess I could use the 11mm F/F followed by the 1.5mm M/M + the 16.5 giving 29mm but this seems a bit complicated!

Just wondering what other folk do - I cant be the only one with this problem. Any thoughts please?

[Guest]

Hi Tom, the 0,5 mm difference can't be that dramatic, but you should try to see how the starrs look like.. But can I ask a question, which SW Coma Corrector are you using ?? is it this one ? https://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html since I see you have a Skywatcher Explorer 200p!!

But I would have done the same like you did, if no spare and adaquate ADAPTER was available.. 

Martin

[vlaiv]

I would go with 28mm extension / combination of extensions. You need to calculate in filters and their optical path, and they usually add about 0.5mm (well I've heard figure of 1/3 of substrate thickness and that is around 0.7mm for 2mm filters, but 0.5mm is good enough).

Also you might find that specs on correct distance are not quite applicable in your specific case (it depends on so many factors, like exact FL of scope that can vary between instruments, ...) so using some spacers to dial in correct distance will probably be good idea. Just start with somewhat shorter distance, and tune it until you are happy with results.

[spillage]

I had fun with mine, it ended up feeling like a rubix cube. I got things close so stripped to add spacers then could not figure out how the bits went back.

I ended up buying a t2 extension set from ebay for about £12 and now have the correct spacing.

spill.

[Tommohawk]

7 hours ago, artem said:

Hi Tom, the 0,5 mm difference can't be that dramatic, but you should try to see how the starrs look like.. But can I ask a question, which SW Coma Corrector are you using ?? is it this one ? https://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html since I see you have a Skywatcher Explorer 200p!!

But I would have done the same like you did, if no spare and adaquate ADAPTER was available.. 

Martin

Thanks Martin - yes thats the one. I've used it with my Canon DSLR for some years with no problems - it's just the ZWO ASI adapter thats foxed me. I'm surprised that ZWO don't supply one as standard!

6 hours ago, vlaiv said:

I would go with 28mm extension / combination of extensions. You need to calculate in filters and their optical path, and they usually add about 0.5mm (well I've heard figure of 1/3 of substrate thickness and that is around 0.7mm for 2mm filters, but 0.5mm is good enough).

Also you might find that specs on correct distance are not quite applicable in your specific case (it depends on so many factors, like exact FL of scope that can vary between instruments, ...) so using some spacers to dial in correct distance will probably be good idea. Just start with somewhat shorter distance, and tune it until you are happy with results.

Hi Vlav - I know the CC has worked well with the DSLR and SW200P, so just a question of replicating this spacing somehow. It must be a common requirement for the ASI1600 which is mostly used for DSOs, and I'm just surprised ZWO dont do one as standard. I'll have a word with Sam at ZWO and see what he says. Just wanted to ensure I wasnt missing something obvious!

5 hours ago, spillage said:

I had fun with mine, it ended up feeling like a rubix cube. I got things close so stripped to add spacers then could not figure out how the bits went back.

I ended up buying a t2 extension set from ebay for about £12 and now have the correct spacing.

spill.

Hi spill - yes something like that might help, though the 5/10/15/20 options still dont quite give the correct 28.5. Nearest is the 10 + my 16.5. I reckon I'll give my 16.5/1.5/11 a try and just leave them screwed together firmly as a single unit - I dont need them for anything else. As Vlav says an extra 0.5 might help anyhow because of the filters effect on the path.

Thanks all, I'll post back when I've tried it out.

[Tommohawk]

Ohh just realised - Vlav you said the filters add to the effective path, not to the requirement, so should be 28mm as you said. Gee I'm a bit slow!

[RolandKol]

Hi Tommohawk

I am in the same "ZWO LEGO puzzle" at the moment, can you please advice which exactly spacer/adaptor solved the issue?

[alexbb]

As far as I know, the SW coma corrector is not that sensible to backfocus, the spot shape towards corners is not uniform at all wavelengths, I believe 1mm in/out won't matter.

My solving for this was to put a ZWO OAG, another M48 ring on the thread (6. in the picture) and a 7.5mm extender between the SW CC and the EFW.

If I remember correctly, I placed the sensor at about 56mm away from the CC and the result is this: https://www.astrobin.com/341636/

The image is from FLO.

[Adam J]

Directly connect the camera male connector to the filter wheel, then use the 21mm spacer included with the camera, then purchase a 7.5mm t-spacer and then connect to the coma corrector giving you a total spacing of 

6.5mm + 20mm + 21mm + 7.5mm = 55mm 

So the only thing that you need that you dont already have is the 7.5mm spacer 

I find this one to be of good quality. 

https://www.firstlightoptics.com/adapters/baader-t2-extension-tube.html

[RolandKol]

6 minutes ago, Adam J said:

Directly connect the camera male connector to the filter wheel, then use the 21mm spacer included with the camera, then purchase a 7.5mm t-spacer and then connect to the coma corrector giving you a total spacing of 

6.5mm + 20mm + 21mm + 7.5mm = 55mm 

So the only thing that you need that you dont already have is the 7.5mm spacer 

I find this one to be of good quality. 

https://www.firstlightoptics.com/adapters/baader-t2-extension-tube.html

Many THANKS!!!!!!!!!!!!

 

[Tommohawk]

In the end I sorted this without having to but any additional parts - but am at work now and cant remember how. If you wait til end of today I can reply by then.

I think the standard kit includes an M48 adapter.

[Tommohawk]

OK the way I did it, using the ZWO adapters provided is:

CC, 16.5mm length 48mm female/42mm male adapter, then  21mm length 42mm extender female to male, then 11mm length 42mm extender female to female, then ASI 1600 with 6.5mm back focus.

Total is 16.5 + 21 + 11 + 6.5 = 55mm

 You shouldn't have to buy any parts, unless maybe some packages didn't come with the adapters I've described above.

[Adam J]

1 hour ago, Tommohawk said:

OK the way I did it, using the ZWO adapters provided is:

CC, 16.5mm length 48mm female/42mm male adapter, then  21mm length 42mm extender female to male, then 11mm length 42mm extender female to female, then ASI 1600 with 6.5mm back focus.

Total is 16.5 + 21 + 11 + 6.5 = 55mm

 You shouldn't have to buy any parts, unless maybe some packages didn't come with the adapters I've described above.

Problem is that you have not included his 20mm thick filter wheel?

[Tommohawk]

34 minutes ago, Adam J said:

Problem is that you have not included his 20mm thick filter wheel?

Details, details. 

We'll spotted! OK so that wasn't how I did it, that's the solution for the colour version. 

I'll go away and think about it again. At the moment I'm overcome with the excitement of deliberately sidestepping Brazil in the football. 

[RolandKol]

No problem Tommohawk as Adam J already told me how to do it.

 

[simmo39]

18 minutes ago, RolandKol said:

No problem Tommohawk as Adam J already told me how to do it.

 

Can you tell me please? need to get it right in my head for when I get mine.

thanks

[RolandKol]

2 minutes ago, simmo39 said:

Can you tell me please? need to get it right in my head for when I get mine.

thanks

I am still waiting for the delivery, but I went as suggested below:

On 27/06/2018 at 10:42, Adam J said:

Directly connect the camera male connector to the filter wheel, then use the 21mm spacer included with the camera, then purchase a 7.5mm t-spacer and then connect to the coma corrector giving you a total spacing of 

6.5mm + 20mm + 21mm + 7.5mm = 55mm 

So the only thing that you need that you dont already have is the 7.5mm spacer 

I find this one to be of good quality. 

https://www.firstlightoptics.com/adapters/baader-t2-extension-tube.html

 

[simmo39]

Just now, RolandKol said:

I am still waiting for the delivery, but I went as suggested below:

 

Cool, think I will have to invest in a 7.5mm spacer.

[RolandKol]

I just googled and found another one, - a bit cheaper, 

but not sure if it will fit...
https://www.altairastro.com/Easy-Grip-7.5mm-T2-Extension-Tube-Spacer.html

[Adam J]

4 hours ago, RolandKol said:

I just googled and found another one, - a bit cheaper, 

but not sure if it will fit...
https://www.altairastro.com/Easy-Grip-7.5mm-T2-Extension-Tube-Spacer.html

It will probably work but I have always liked the machining quality of the Baader parts, notably their threads, hence why I recommended it.

[Tommohawk]

I fudged my earlier reply by forgetting the filter wheel, but I say again you shouldn't need to buy any extra parts. Unless maybe some packages are different to those I received. 

Camera is 6.5 then 20mm filter wheel, then 1mm male to male connector, then 11mm (female both ends) then 16.5 which has 48mm female thread at on end and connects direct to SW CC.

In the drawing below, taken from ZWOs website, its camera then EFW then parts 9, 7, 8 then then CC.

It's probably not the fewest part solution but it is the fewest £ solution!

1. M43-T2 adapter 

2. EOS-T2 adapter 

3. 2”Filter (optional)

4. 1.25” T-Mount 

5. 1.25” Filter (optional)

6. M42-1.25” Filter (optional)

7. T2 extender 11mm

8. M42-M48 extender 16.5mm

9. T2-T2 adapter

10. EFW mini

11. EOS adapter for EFW+1600

 

[simmo39]

11 hours ago, Tommohawk said:

I fudged my earlier reply by forgetting the filter wheel, but I say again you shouldn't need to buy any extra parts. Unless maybe some packages are different to those I received. 

Camera is 6.5 then 20mm filter wheel, then 1mm male to male connector, then 11mm (female both ends) then 16.5 which has 48mm female thread at on end and connects direct to SW CC.

In the drawing below, taken from ZWOs website, its camera then EFW then parts 9, 7, 8 then then CC.

It's probably not the fewest part solution but it is the fewest £ solution!

1. M43-T2 adapter 

2. EOS-T2 adapter 

3. 2”Filter (optional)

4. 1.25” T-Mount 

5. 1.25” Filter (optional)

6. M42-1.25” Filter (optional)

7. T2 extender 11mm

8. M42-M48 extender 16.5mm

9. T2-T2 adapter

10. EFW mini

11. EOS adapter for EFW+1600

 

Yep that adds up. As you say a bit long winded but works out of the box!

[RolandKol]

On 27/06/2018 at 10:42, Adam J said:

Directly connect the camera male connector to the filter wheel, then use the 21mm spacer included with the camera, then purchase a 7.5mm t-spacer and then connect to the coma corrector giving you a total spacing of 

6.5mm + 20mm + 21mm + 7.5mm = 55mm 

So the only thing that you need that you dont already have is the 7.5mm spacer 

I find this one to be of good quality. 

https://www.firstlightoptics.com/adapters/baader-t2-extension-tube.html

1

Does not fit... that 7.5mm T2 extender does not catch SW Coma Corrector threads, they are exactly the same size.
 

I guess this one is needed... "Female to Male" 48 to T2
https://www.365astronomy.com/t2-m48-converter-ring-with-female-m48-thread-and-male-t-thread-7mm-length.html

Edited July 5, 2018 by RolandKol

[Adam J]

3 hours ago, RolandKol said:

Does not fit... that 7.5mm T2 extender does not catch SW Coma Corrector threads, they are exactly the same size.
 

I guess this one is needed... "Female to Male" 48 to T2
https://www.365astronomy.com/t2-m48-converter-ring-with-female-m48-thread-and-male-t-thread-7mm-length.html

is the SW coma corrector m48? not T2? Got to admit I was using the Baader MPCC MK3. If it is t2 and just will not fit...thats odd.

Edited July 5, 2018 by Adam J

[RolandKol]

On 05/07/2018 at 17:55, RolandKol said:

I guess this one is needed... "Female to Male" 48 to T2
https://www.365astronomy.com/t2-m48-converter-ring-with-female-m48-thread-and-male-t-thread-7mm-length.html

 

Just confirming, Skywatcher Coma Corrector and ZWO filter wheel are now properly connected, using the T2 >48 converter ring.
Will check focusing tonight.

Many Thanks all for help  
 

P.S. went out, preparing myself for Veil Nebula hunt