Making the most of what aperture you have

[M110]

So, I am currently very constrained by storage space and so larger apertures are basically out of the question for the time being. I have been thinking about ways to get the most out of the aperture that I do have - I am using a Skymax 102, which meets the space requirement brilliantly but there's not a huge amount of aperture to play with. Especially as this is my only telescope currently and is used for observing all types of targets including DSO's (I know that's not it's forte but we make do with what we have).

One idea is to invest in a dielectric diagonal - RVO have an Altair one for £65 that claims 99% reflectivity, which should be about 4% above that of the stock Skywatcher one I am currently using. Can anyone comment on whether this difference is actually noticeable for visual observing?

Are there any other items or tricks that would help maximise the light gathering ability of a small aperture instrument?

[michael.h.f.wilkinson]

The difference will be hard to spot. I have two 2" diagonals: a 99% reflective one and a 96% reflective filter-switch diagonal. It is near impossible to see any difference (except that the filter-switch diagonal won't come to focus in my little frac )

[John]

I agree with Michael, the diagonal upgrade will not be noticable in terms of light transmission.

My advice would be to get a UHC filter to help increase the contrast of nebulae and also to try and get the scope under dark skies when you can - it is a nice and portable one

[vlaiv]

16 minutes ago, M110 said:

So, I am currently very constrained by storage space and so larger apertures are basically out of the question for the time being. I have been thinking about ways to get the most out of the aperture that I do have - I am using a Skymax 102, which meets the space requirement brilliantly but there's not a huge amount of aperture to play with. Especially as this is my only telescope currently and is used for observing all types of targets including DSO's (I know that's not it's forte but we make do with what we have).

One idea is to invest in a dielectric diagonal - RVO have an Altair one for £65 that claims 99% reflectivity, which should be about 4% above that of the stock Skywatcher one I am currently using. Can anyone comment on whether this difference is actually noticeable for visual observing?

Are there any other items or tricks that would help maximise the light gathering ability of a small aperture instrument?

Every little bit will help but to which extent? So yes, get a good diagonal if you have the funds for it, and get good set of eyepieces if you have funds for it - look for eyepieces that give you most light transmission and contrast.

But much much more can be achieved with tuning "sensor" and conditions rather than light gathering instrument. 4" aperture is potent one although today we hear things such as 8" is minimum for DSO. So optimize for stray light, get away from light pollution as much as you can, get dark adapted, "learn to observe" if you haven't already (I guess that is continuous process - one never fully learns) , check your forecast and aim to observe in high transparency nights, avoid the Moon.

All of that can and will have bigger impact on what you see then changing the diagonal for slightly better one. You can test this your self - find threshold DSO - observe with diagonal - then without it (it will put a bit of a strain on your neck, but try to get as comfortable as you can - lean back in appropriate chair and maybe put a pillow or something to rest your head on). And see how much difference it makes.

[Stu]

I would agree with the comments above. There probably will be very marginal difference in the performance, and there is plenty more you can do to help see objects better.

Most of my observing is with a 4" frac, which has the benefit of being a shorter focal length and so I am able to use larger exit pupils. This really does help when using filters to see faint DSOs.

So, I agree with John regarding getting a UHC filter. If you do, then using it with a 32mm or even 40mm Plossl is likely to give best results. The 40mm will not increase the field of view but will give you a brighter image over the 32mm.

Get to as dark a site as possible, shield yourself from any street lights and try to keep you dark adaptation, chuck a towel over your head if necessary, whatever you need to do.

[M110]

Thank you all for the advice - I am already doing what I can regarding dark skies and will be heading out of town to a darker site this evening for some observing hopefully

I had thought about filters but didn't realise there were ones for visual observation as well as imaging - I will put a UHC filter on the 'to buy' list.

Clear skies,

Alex

[25585]

When you go to dark sites, if you have a car you could make it into an observatory. Roof rack, awnings, a hatch that opens vertically covers top light. Easy to hang side screen down. 

OIII filter may be too dark for a 4 inch aperture, but would brighten nebula. What FL or ratio is your scope?

[mikeDnight]

6 hours ago, M110 said:

 

Are there any other items or tricks that would help maximise the light gathering ability of a small aperture instrument?

Don't underestimate the ability of a 4" scope. One thing that really does help when it comes to teasing out maximum performance in any scope, is to block out stray light that hits the eye from your surroundings. Stray light prevents the eye from attaining true dark adaption, even at relatively dark sites. By using a dark blanket or hood to cover your head and eyepiece your eye will produce visual purple, which greatly increases the eyes sensitivity to low light levels. It takes about 20mins for the eye to become fully dark adapted but its worth the wait. Try observing the Pleiades, or any other dso within the range of your scope, for 20 to 30 minutes while under such a blackout hood and you'll definitely notice the increase in detail.