Stupid question time - which filter is which!

[dannybgoode]

So dusting down the scope for what will hopefully be an imaging session this evening and going to have a go at some narrowband work.  So stupid question; I loaded up my filterwheel some months ago and cannot say for certain which order I put the filters in.  I think I have them Ha, SII and OIII (Baader ones if it helps).  I know OIII is the bluish one however is there an easy way to tell which is Ha and which is SII?!

[vlaiv]

No that I know of.

Ha and SII are so close that there will be no definite difference in color - both will look deep red and have strange bluish/greenish interference reflections.

Do you have separate Ha or SII filter - something old that you can use?

Putting two filters one on top of another will either pass the light or block the light - two of the same should pass the light while two different ones will block the light - so I was thinking visual inspection - place for example 2" Ha filter in front of opening of filter wheel and look by naked eye - if you see something - you have Ha filter selected, if not - it is any other (except broad band filters).

Maybe open filter wheel and check markings if they are mounted filters?

[dannybgoode]

34 minutes ago, vlaiv said:

No that I know of.

Ha and SII are so close that there will be no definite difference in color - both will look deep red and have strange bluish/greenish interference reflections.

Do you have separate Ha or SII filter - something old that you can use?

Putting two filters one on top of another will either pass the light or block the light - two of the same should pass the light while two different ones will block the light - so I was thinking visual inspection - place for example 2" Ha filter in front of opening of filter wheel and look by naked eye - if you see something - you have Ha filter selected, if not - it is any other (except broad band filters).

Maybe open filter wheel and check markings if they are mounted filters?

Thanks @vlaiv.  Yes it's a problem and no - unfortunately these filters are all I have.  Will have to look at the filters for any markings I think - no biggy and I have plenty of other things I need to get working for tonight (like the whole of Astroberry/KStars/EKOS!).

[MarkAR]

Might have to do some trial shots on a nebula if there's no markings. 

[dannybgoode]

27 minutes ago, MarkAR said:

Might have to do some trial shots on a nebula if there's no markings. 

Going to try some NB imaging tonight. How will I be able to tell from the light frames which is which?

[vlaiv]

Just now, dannybgoode said:

Going to try some NB imaging tonight. How will I be able to tell from the light frames which is which?

Not sure if you need to during imaging session - just image with all three filters.

Once you've stacked your data - Ha is the one with the strongest signal (almost all targets out there have significantly stronger Ha then other lines as Hydrogen is the most abundant element and easily excited).

[dannybgoode]

Just now, vlaiv said:

Not sure if you need to during imaging session - just image with all three filters.

Once you've stacked your data - Ha is the one with the strongest signal (almost all targets out there have significantly stronger Ha then other lines as Hydrogen is the most abundant element and easily excited).

Thanks - that makes sense. Will run a sequence tonight and have a play. Assuming it stays clear that is - as is usual it’s been forecast nailed on clear skies tonight and tomorrow until I’ve got the kit pretty much sorted and now it looks like nailed on cloud...

[MarkAR]

Maybe a target like The Wizard could be good. Ha pretty strong, Oiii good and Sii faint.