kit lens replacement?

[Trucker360]

i need something either a) better or b) a 8" astrograph. currently i have a kit 75-300mm canon lens. i need something better. id prefer it to have 58mm front threads as i just bought 2 weeks ago a kolari uv/ir cut ha pass filter. camera is a 450d full spectrum.  

[LaurenceT]

A highly recommended camera lens for deep sky astrophotography is the Samyang 135mm F2 lens. I have the Sony version and although I haven't yet used it for astrophotography I have used it for general photography and it's the sharpest lens I own, 135mm fast primes usually are. Unfortunately the filter size is 77mm.

The Rokinon 135mm F/2 was Built for Astrophotography (Examples) (astrobackyard.com)

[Uranium235]

Its all here:

 

Its possible to use your exisiting filter by using a step down ring, which would slow the lens to about F2.5ish - might actually work in a positive way for you as youre stopping down without using the aperture blades (no star spikes)

[PeterCPC]

+1 for Samyang 135mm.🔭

[michael.h.f.wilkinson]

Just got one of those 135 mm lenses myself. Fingers crossed for first light Wednesday night

[Trucker360]

14 hours ago, Uranium235 said:

Its all here:

 

Its possible to use your exisiting filter by using a step down ring, which would slow the lens to about F2.5ish - might actually work in a positive way for you as youre stopping down without using the aperture blades (no star spikes)

I'm going to need more explanation and or pics. I don't get how that sounds good. 

[LaurenceT]

7 hours ago, Trucker360 said:

I'm going to need more explanation and or pics. I don't get how that sounds good. 

Specifically which bits sound negative to you?

[Trucker360]

6 hours ago, LaurenceT said:

Specifically which bits sound negative to you?

Not negative persay, confusing. 

1) this adapter ring thing. Sounds counter productive. 

2) I like close up action. This is less focal than my current lens.

 

3) another person said stop down my current lens to fix coma, but I'm not sure what to stop down to. 

[alacant]

Hi

Yeah. Even stopped to f8 or smaller, the bundled 75-300 falls short in many areas, especially as you move toward the 300mm end of the zoom and on stars, well...

If you want to stick with camera lenses at the longer end of your current range, the old Russian Tair 3s or 3a (300mm f4.5) triplets are good and available economically on the used market. Your filter with a 72 to 58 stepping ring would give you around f5. Nice. 

If you want closer still and have a suitable mounting, perhaps your second idea, the 8" telescope, is the way forward.

Cheers and HTH

 

Edited December 8, 2021 by alacant

[LaurenceT]

1 hour ago, Trucker360 said:

Not negative persay, confusing. 

1) this adapter ring thing. Sounds counter productive. 

2) I like close up action. This is less focal than my current lens.

 

3) another person said stop down my current lens to fix coma, but I'm not sure what to stop down to. 

I'm sorry but I can't find a reference to an adapter ring in the link I supplied. In that link Trevor Jones says the lens is not suitable for small DSO's and most galaxies but he does give a fairly impressive list of suitable targets.

[900SL]

Askar FMA 180 will give you a similar reach to the kit zoom on a CMOS body, or the FMA 230 if you want to go a bit further. 

 

FMA 180 is very compact and light, good sharpness, some blue halo around stars that can be dialed out with a filter.

 

Samyang 135 f2 is excellent for wider field, example of mine here, cropping in on Pleiades at f2.8:

 

  

 

 

 

Edited December 9, 2021 by 900SL