Which telescope focal length optimal for DSO nebula etc ?

[2Jules]

Hi all fellow astronomers. I am new to the forum and fairly new to astrophotography.

Last summer I invested in a HEQ5 mount and Williams Optics Redcat51, ASIair+, guidescope and ASI533MCpro. Most interested in images of nebula in narrowband and the occasional galaxy if large enough.  Got some good images of the Veil nebula using Optolong Enhance filter from London, during that really hot spell last summer.  Very pleased with the tracking using HEQ5mount with Rowan upgrade. Can do 300 seconds easily. Now thinking about another telescope with greater focal length, but still mostly interested in narrowband DSO or  monochrome LRGB.    I use Pixinsight.

Question : what telescope focal length would you recommend for objects such as Veil, Heart Orion nebula, M31, M33 and such like?      Also thinking of investing into a ZWO ASI 2600MMpro and filter wheel etc. Expensive but should last a long time?

Budget for next telescope around £2000 - 3000. I am interested in a Newtonian perhaps because I don't have one and they seem to be faster. A little concerned re collimation, but I am sure I could learn this. Or just stick with a refractor? I don't want anything too heavy since want to stick with my current mount.

Apologies if discussed before? Thanks

[ollypenrice]

On your budget I would consider a RASA 8. The focal length is only 400mm but the large aperture gives good resolution of detail and the speed, at F2, is simply phenomenal.  When I started using this scope I saw it as a widefield nebula (dusty and emission) tool but, if fact, it is doing remarkably well on small targets requiring good resolution. There is a catch: it can't be used with a filterwheel so you can use it with straight one shot colour or as one shot colour via a dual or triband filter for narrowband. Also I'm not sure about the HEQ5 with the RASA. The speed of the system, though, means you can happily work in short exposures. I've never had an HEQ5.  Others may come in on this.

A word on your requirements. You say, '...such as Veil, Heart Orion nebula, M31, M33 and such like? '   I don't really see how these can be grouped together. The Veil is nine times larger by area than M33. For M31 we needed a 2 panel mosaic at 400mm with an APSc chip. At a metre, with a full frame CCD, I also needed a 2-panel.

Olly

 

 

[barbulo]

Hi and welcome to SGL. 

I am far from beign an expert but expending somebody else's money is funny. 

Seriously, I regularely think what piece of equipment would I buy if I had no budget limitations and I would say the Espsilon 130 + ASI2600MM.

[alacant]

6 hours ago, 2Jules said:

Veil, Heart Orion nebula, M31, M33

Hi

You already have a good choice for some of these. For the rest, perhaps one of these. It won't trouble the heq5 and you'd still have loadsa € left for a monochrome camera, filters and other stuff.

Cheers and HTH.

Edited April 25, 2023 by alacant

[900SL]

90mm f6 refractor is a sweet spot for me with the 533MC and a 0.8x reducer

Pretty fast at f4.6, good FOV for many DSO targets, pixel scale 1.8"/px, no collimation issues, not too demanding on tracking or guiding etc

 

[Elp]

Think you need to have a ponder a bit more about the targets you want to shoot. With your existing camera a Samyang 135 will frame all of them very well barring M33. A larger scope will likely mean longer focal length but you'll have better resolution than the Redcat. 

I'd recommend you have a play around with Telescopius and their telescope simulator page to check framing on targets. If you do end up with a longer focal length scope there's nothing wrong with mosaics if you've got the time and patience to image them, a super fast scope helps with this aspect.

Edited April 25, 2023 by Elp

[2Jules]

Thank you

I recently retired and also came into some money due to a family member passing away. Hence the  budget.  I have a Celestron 8 SCT which is about 25 years old gathering dust in my shed,  which I took off that alt az arm goto thingy and put a vixen on it and attached it to my HEQ5 mount : better but still not great imaging or visual.  Tried collimating it with stars in the dark. Still not great.

What do I want to image? most things. The limitation in my opinion is the sky here. 

I went to Tenerife a few weeks ago. Have been there a few times. Mount Teide National Park.  You can't take much on a plane. Good darks skies and about 7000 feet up. Quite a strong wind though.  But now having problems with the Saharan sand : "Calima". this is supposedly only blowing on rare occasions a couple of months a year in the summer but strangely now is there more frequently including April, which interferes significantly. This is very disappointing. 

Yes I have been playing around with Telescopius. Very useful.