Finally bought my first telescope (Heritage 150P). I have questions!

[albert91tgn]

Hello everyone! 

I've always been fascinated by the sky as I grew up in a very small village in Spain with wonderful views (I could often see the milky way from my bedroom). I moved to London at 18, and last year after moaning to my girlfriend about how much I missed the stars she organised to hire a Skywatcher 200P from Seb Jay (darkskytelescopehire.co.uk) and we spent a few days on the best dark sky site I could find at car distance (Wiveton Downs in Norfolk) . It was cloudly/rainy most nights and was ready to give up, but the last night had broken clouds and I was blown away. Despite only having the stock eyepieces, no previous experience, suboptimal weather and no planets visible, for the first time I saw some DSOs (Andromeda, Orion and even the ring nebula!) and I instantly knew I had to buy a telescope. 

Now, I've been putting this off since then last for several reasons. We live in a shared flat and don't have much storage space, we live in zone 2 in London (Acton, if you're near please contact me!) and the light pollution is insane and the only telescope I can realistically own, store and travel with that I liked was the heritage 130p which seemed like too much a downgrade from the 200P I had already tried. It was only this month with the release of the Heritage 150P and the significant savings I've built over lockdown that I've bitten the bullet and purchased it. So far I haven't been able to try it at night as it's been cloudy for the last few days, but just by testing it on my street I hated the 10mm so I purchased a BST 8mm.  I know the general advice for a beginner is to just replace the 10mm and then use the scope for a bit until you decide what's next, but I want to invest a bit more (given I have to travel to use it I won't be able to use it everyday hence I want to make the most of these trips) and I see a few options (listing them in the order of importance I perceive them):
 

1. A light pollution filter (looking at SVBONY UHC or CLS) given that I'll mostly be using my telescope in the outskirts of London
2. A DIY light shroud (again, light pollution. My garden is surrounded by street lamps)
3. A BST 5mm for planets (seeing Saturn an Jupiter is my girlfriend's top priority and I'm not sure the 8mm will do)
4. A BST 12/15mm to fill the in-between of my BST 8mm and the stock 25mm 
5. A 1.5x barlow lens to get a 6mm and a 17mm out of my existing eyepieces

Are these the right purchases? If so, in what order of priority would you get them?

Edited July 13, 2020 by albert91tgn

[Ricochet]

My order would be:

1. DIY light shroud. I don't think there is any downside to having one,so go for it.
2. 5mm BST. Jupiter and Saturn are in the sky now, so you will want to get this before they are too low in the sky to observe. In addition, as it will give you a 1mm exit pupil, this focal length should give you a high power option for viewing star clusters. Increasing magnification to this level will significantly darken the background sky, whilst star brightness should be pretty similar to lower magnifications.
3. 12mm BST. A 2.5mm exit pupil is a good option to have. Under light polluted skies it might be less used than "normal" but it will still be a good option to have. The 15mm is reportedly not as well corrected as the 12, so the 12 is the option to go for.

With regards to the barlow, a 2X might be useful as it would effectively give you 4mm and 6mm options, which may be useful as the planets are so low this year and the atmosphere will limit the magnification that can be used, however, I'm not sure that it is essential.

Light pollution filters are mostly aimed at sodium lighting, with the increase in LED lighting, they are generally becoming less effective. Good ones might make a very small difference on some targets, cheap ones are likely to be pretty much useless. UHC and OIII filters are useful on emission nebula, but the same rule applies, cheap ones with a bandpass that is too wide will not perform as well as they should. Under heavily light polluted skies I think the narrower bandpass of an OIII filter is more useful so that is the one I would look at, although I expect you would only find it useful on the Orion, Ring and possibly Dumbbell Nebulae without going to dark sites.

[albert91tgn]

Thanks Ricochet for the comprehensive answer. I've ordered the 5mm BST and a big piece of foam that by my calculations should allow me to do a light shroud that sticks on the inside and hides neatly inside the scope when folded. 

 

[Ricochet]

Good choices, that foam looks like it should work to me.