Alternative Apochromatic to RedCat 51

[stevenson166]

Hi All, I have the following kit..

Canon EOS 800D

Skywatcher Star Adventurer Pro ( Awaiting delivery)

Samyang 2.8/14mm Lens

Manfrotto 190XPRO Manfrotto MHXPRO-3W SVBONY CLS clip on filter

The following APO i have seen that gives fantastic imaging results was a William Optics v1.5 RedCat 51 APO f/4.9

my question is can anyone recommend any other APO , so that i have a choice ? or  any other bits of kit that would complement my gear. My aim is to take nebula and deep sky images

Thanks Paul

[Stuf1978]

Have a look at the Sharpstar EDPH II, it's cheaper than the redcat too 👍

[bottletopburly]

https://agenaastro.com/askar-40mm-f-5-5-triplet-apo-lens-guidescope-fma180.html possibly

[Seelive]

Or, for the same cost, you could go for the Canon 200mm F2.8 (if you can still get one). It can be used wide open with a crop sensor camera and hence cut the exposure times by more than a half.

[ollypenrice]

36 minutes ago, Seelive said:

Or, for the same cost, you could go for the Canon 200mm F2.8 (if you can still get one). It can be used wide open with a crop sensor camera and hence cut the exposure times by more than a half.

You can't safely compare F ratios at different focal lengths.

Oly

[vineyard]

I'm quite happy with my Evoguide50ED with a Skywatcher Evo Field Flattener.  Works really well & is much cheaper than a Redcat.  Some basic quick images here.  (Have also figured out a way to use 1.25" filters with it subsequent to this post).

.

[rickwayne]

Rule of thumb for astro imaging is not to exceed 1/2 the mount's rated capacity. So we're talking a max total optical-tube-assembly+camera weight of 5.5 lbs..

The Rokinon 135 f/2 is very highly recommended. If you want to go longer without shattering the bank, you might be able to pick up a Pentax 300mm f/4 for a not-absurd amount of money. There are quite a few beautiful images you can make at pretty modest focal lengths. I would recommend starting with kit that's lightweight and not too long, to minimize basic problems, and honing your acquisition and especially your processing workflows and skills before going deeper. Especially with Andromeda and the Orion Molecular Cloud Complex easily visible, you can start pretty wide and amaze yourself.

One example of difficulties that mount with the focal length: unless you're already an accomplished visual astronomer you will not believe how difficult it is to simply get a dim target framed with a long lens or telescope. Thirty dollars spent on one of these helped rescue my sanity: red/green dot sight for hotshoe mounting. Until I got a GOTO mount I used it every time, I got so that I could point a famously-dim 500mm mirror lens and only take half a dozen tries or so to frame something with it. (A less famously-dim astronomer would no doubt have helped, perhaps you're one of those lucky ducks.)

 

[Adam J]

7 hours ago, stevenson166 said:

Hi All, I have the following kit..

Canon EOS 800D

Skywatcher Star Adventurer Pro ( Awaiting delivery)

Samyang 2.8/14mm Lens

Manfrotto 190XPRO Manfrotto MHXPRO-3W SVBONY CLS clip on filter

The following APO i have seen that gives fantastic imaging results was a William Optics v1.5 RedCat 51 APO f/4.9

my question is can anyone recommend any other APO , so that i have a choice ? or  any other bits of kit that would complement my gear. My aim is to take nebula and deep sky images

Thanks Paul

Askar FMA180 or ACL200 are good options. 

Adam 

[ollypenrice]

11 hours ago, Seelive said:

Or, for the same cost, you could go for the Canon 200mm F2.8 (if you can still get one). It can be used wide open with a crop sensor camera and hence cut the exposure times by more than a half.

 

11 hours ago, ollypenrice said:

You can't safely compare F ratios at different focal lengths.

Olly

This comes up regularly. To clarify, the formula stating that exposure time increases as the square of the F ratio is predicated on having a fixed focal length and a variable aperture, meaning that aperture is the 'active ingredient.'  On top of that we have to consider pixel size because what really determines exposure time is the ratio of objective area to pixel area. And on top of that (oh no!) we have to consider 'regions of interest.' At short focal lengths we may end up capturing an enormous amount of sky in which we are not interested and concentrating plenty of light from our target onto too few pixels.

Professional telescopes are often of slow F ratio but work very quickly because they have large aperture and large pixels.

Olly

Edited October 25, 2020 by ollypenrice

[Whirlwind]

A more expensive option (about twice the price after taking into account the flattener and reducer) would be the Vixen FL55 which would have a comparable focal length.   There is also the new Radian Raptor from Optcorp which I think is based on the same optics of the Sharpstar (although apparently they only take the premium lenses).  However the latter is new and untested and would likely need to be imported.

[johngm]

I use this with my AZ-GTI mount in EQ mode and works a treat

https://www.altairastro.com/altair-60-edf-doublet-refractor-telescope-450-p.asp. Its less than £500 with the flattener, 200 quid cheaper than the red cat.

Here is shot of M31 i took with it from 4hrs in my borttle 6, 19.5 SQM backyard sky, using an unmodified canon 100D and Asronomik CLS cip filter. Not the best processed image, but will give you some idea 

[gorann]

18 hours ago, Seelive said:

Or, for the same cost, you could go for the Canon 200mm F2.8 (if you can still get one). It can be used wide open with a crop sensor camera and hence cut the exposure times by more than a half.

Or the Canon EF 300 mm f/4. Both these Canon lenses will gather more than twice the light of a Red Cat and will cost you less if bought used. They are apochromats with flat fields. I have had some good experience with the 300mm f/4 on a Star Adventurer. Brought it to Australia a year ago, and you can see the images on my Astrobin (in my signature below) if you go down to Decenber 2019. I bought the lens on ebay. Be sure to go for the old version without image stabilizer (which is also cheaper).

[stevenson166]

Thanks for all the replies...please keep them coming...as i have zero experience i just want to share my first RAW pic...i have taken about 20 with the setting of 

RAW

800 ISO

BULB

2.8 with my Samyang and the CLS filter attached

Image pending..sorry

Edited October 25, 2020 by stevenson166

[nfotis]

If you plan on continuing with Canon lenses, the Samyang/Rokinon 135/2 and the Canon 200mm/2.8 are excellent lenses, and quite fast.

 

N.F.

[AstroFin]

Another vote for Samyang/Rokinon 135mm ! It's a very sharp, portable and fast (!) lens, yet the focal length is still quite forgiving (in terms of tracking accuracy).  The field of view is so wide that objects in the night sky are generally quite easy to find. 

Here's my recent shot of the California Nebula with just 1hr 15min of exposure. Bortle 5. I'm also using the Star Adventurer.

https://www.astrobin.com/full/a2i42a/0/

[stevenson166]

I bought the Altair Astro 66mm ED-R for £200...should be ok to start 😀

[amateur-astro]

Just browsing the thread and realising it's from 2020, just a quick one if your still active,  how did you find the Altair Astro 66mm ED-R?, was it worth the money.