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2 nights in one week? fantastic!


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1 hour ago, SuburbanMak said:

I picked the Owl up on the basis of its distinctive shape - I use a Baader Neodymium filter pretty much all the time & often forget to switch in my OIII or UHC. Will have to give them arty, but then I’ll be back there hunting M108 down anyway…

 Generally I find the OIII & UHC dim the view to an extent that I prefer without.
Have enjoyed them on the Lagoon, Swan & Triffid nebs in the summer though & last night on M42.  They pull out different features so your brain builds up a layered view - like a bio-astrophoto! 

I suspect it’s the long focal ratio on the Mak which may be causing your issues with the filters. It’s hard to get large enough exit pupils so the image will be dimmer. As an example, a 32mm Plossl in an f12 Mak gives an exit pupil of 2.6mm, whereas in an f5 newt (such as the 130p) it gives 6.4mm. Yes you get lower mag but a brighter image. It’s even worth considering a 40mm Plossl in the Mak (if you haven’t already) as it gives 3.3mm, a useful increase even though the field of view remains the same.

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  • 3 weeks later...
On 09/01/2022 at 18:38, Stu said:

I suspect it’s the long focal ratio on the Mak which may be causing your issues with the filters. It’s hard to get large enough exit pupils so the image will be dimmer. As an example, a 32mm Plossl in an f12 Mak gives an exit pupil of 2.6mm, whereas in an f5 newt (such as the 130p) it gives 6.4mm. Yes you get lower mag but a brighter image. It’s even worth considering a 40mm Plossl in the Mak (if you haven’t already) as it gives 3.3mm, a useful increase even though the field of view remains the same.

Thanks Stu - I missed your comment earlier in the month. Good tip, have to confess I haven't really got my head around exit pupil and its impact on observation. I'll look out for a 40mm Plossl & give this a go.  Typically using a 24mm Baader Hyperion in the Mak as my deep sky hunter & its done good service up to now. Am after the fainter UM galaxies a challenge (M101, M106, M108 & M109 all hiding from me over a few sessions...) so this tip on squeezing out the last little bit of performance is very gratefully received! 

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