31mm filters

[Tommohawk]

Hi all

Am looking to make the jump to mono for both DSOs and planetary. Will probably end up with an F4 Newt and ASI1600mm, and am looking at filter options. I've never had a wheel or filters or seen one in the flesh, so just trying to work out how it all goes together.

Looks like 25mm filters screw in, but at F4 I think I'll need 31mm filters - according to ZWO. But how do these fit in the wheel? Do they just sit in there? Looks like they would would float about a bit, no?

[Davey-T]

31mm are basically a 1.25" filter without the metal thread bit, they're usually held in with fiddly little screws and O rings.

Cameras with built in filter wheels are generally OK with 1.25" as they're close to the sensor.

A few people with the ASI1600 on here so no doubt they can offer advice.

Dave

[groberts]

I''ve recently been in the same situation moving from DSLR to the ZWO1600MM-Cool and am still on the learning curve.  I'm not going to pretend it's been easy but it's now starting to click and the camera is very good + great fun, I've particularly enjoyed narrowband imaging.  I purchased the ZWO package of camera + x8 EFW and LRGB + HA OIII and SII filters.

My William Optics GT81 + field flattener comes in at f3.8 and does require 31mm filters, can't remember where the 25-31 cut-off point is but I I think it's just above this speed and I'm sure you'll need the 31mm filters too at f4 - in any event better safe than sorry.  The 31mm filters sit in a depression and are held in place with three very small screws and composite washers.  Dave's correct they are very fiddly to fit - best put a couple of hours aside and find a method that works for you.  I rested my wrist on a cushion for stability and used tweezers and a watchmaker's screwdriver etc.  after the first two it gets a little easier!  

Once set-up I've found the EFW to be a breeze to use + good results.  Notwithstanding, it's a whole new ballgame compared to DSLR and creates a lot of data that requires lots of PC memory and processing power.  For me the clincher over CCD is the ability to get the data with shorter exposures with using this camera, thereby making this type of imaging more practical for UK skies i.e. lots of cloud!  

 A few of my EFW set-up pictures are shown + some links to my early experiences with the camera and EFW.

Good luck + hope this helps - Graham

 

https://watchthisspaceman.wordpress.com/2017/03/28/first-light/

https://watchthisspaceman.wordpress.com/2017/04/11/brave-new-world/

https://watchthisspaceman.wordpress.com/2017/05/02/a-new-palette/  

 

[Davey-T]

After dropping a screw into the innards of the wheel I found it easier / safer to remove the carousel to fit the filters.

Dave

[Tommohawk]

Hey thanks guys thats really helpful - Graham thanks for taking the trouble to post the pics, and the links - I read them all and very informative they are too!

Dave - your point about the dropped screw and removing the carousel is a great tip.

One other point this makes is that with 31mm filters you probably dont want to be taking them in and out too often. I had in mind to get just a 5 postion wheel for LRGB and swap with NB as required. But 8 position obviously allows to put NB in at same time and just leave it. Hmmm.

I also intended to go for a manual wheel - keep it simpple as possible - but I wonder if EFW would be better for automated sequences.

But - if refocusing is required between filters, might as well move the wheel manually, no?

Talking of focusing reminds me of another point I wanted to raise. I always spend forever focusing, but if doing planets taking 5 mins to refocus between filters is going to desyncronize the image sequence, isnt it? How do folk cope with that?

[Tommohawk]

Oh one other thing re the electric filter wheels - is it possible to move the wheel manually ie to override the electric drive?

[Davey-T]

Depends how much money you're planning on spending, an electronic filter wheel is a good thing as is an electronic focuser then with a bit software you can autofocus between filters.

Due to the crap UK weather it's not generally a problem as I do one filter per night 

Dave

[Davey-T]

2 minutes ago, Tommohawk said:

Oh one other thing re the electric filter wheels - is it possible to move the wheel manually ie to override the electric drive?

Not with my Atiks.

Dave

[Davey-T]

Are you set on the ASI1600 ? only ask as the Atik capture software works really well to control the camera and filter wheel.

Dave

[Tommohawk]

OK thanks Dave - I dont think I'll have autofocus for a while and I dont like the idea of getting stuck if the EFW fails + extra cables etc so maybe will keep with manual wheel.

Not 100% set on ASI1600 but 99% maybe! Seems to offer best bang for buck especially as more pixels/buck.

[Davey-T]

19 minutes ago, Tommohawk said:

OK thanks Dave - I dont think I'll have autofocus for a while and I dont like the idea of getting stuck if the EFW fails + extra cables etc so maybe will keep with manual wheel.

Not 100% set on ASI1600 but 99% maybe! Seems to offer best bang for buck especially as more pixels/buck.

It also turns out a lot of data if you take short exposures so make sure you've got enough HD space for them.

I think a 60 sec exposure takes up as much space as a 20 minute one so 20 times as much disc space for the same image, may be different for the ASI but that's the way my QSI works.

Dave

[Tommohawk]

Good point.

In the past I've kept all my RAW files on the HDD (500GB) but probably I'll have to move them over to an external drive after processing. I've got used to doing this with planetary cos at 200-300 fps you get some truly monstrous files, so I just move them to a 1TB external drive when I'm done. I guess that'll fill up soon enough though!