Baader semi apo filter

[GSO]

Hi all, newbie here, I did try a search on the topic but couldn't see any results...?

Has anyone used this Baader filter - I'm wondering if it would improve the performance of an achro?

Thanks

[MattT]

While the Badder semi-APO filter doesn't improve the performance of the scope...it improves the image by removing some of the out of focus violet, at that end of the spectrum.

Works well in a 6" f8 achro for Jupiter and the Moon....anything else and the results are not as good.

Took too much light away from a 4" f5 Achro and my present scope, 6" f12 Achro there is no real difference.

Some say a yellow filter is just as good...except it makes everything yellow, the semi-apo leaves it more natural.

What scope do you want to use it in?

Matt

[speedyjim]

Yes and No...It slightly reduces light transmission so if looking at clusters it's not worth it.... On my Na140ss it works well because it's design already reduces CA due to the f11 objective and petz lens design...

As other poster mentioned is better on Jupiter etc BUT...

the baader 495 Long pass filter is Soooooo much better. It makes a huge difference! OK everything goes yellow but my god your achro will focus so sharply you will see so much more detail.. Great for Jupiter and saturn... Basically an APO in yellow..lol. Highly recommended on big fast achros

[AG Hybrid]

My Semi Apo filter took a lot of light away from my ES 102 achro. Also turned stars that already had no violet fringe into vomit color. I just bought a 6" Mak instead for the high power views and use the 4" for low power rich field stuff that is not really affected by CA.
A rather expensive filter that just sits in my eyepiece case at the moment. I don't foresee myself picking up a big achro anymore now that I have a Mak.

[Wavytone]

Agree with AG - don't waste your $ - buy a mak. In particular the Skywatcher 150 or 180mm f/15 ones will give ostensibly perfect images at high power, free from chromatic aberration. These scopes are a bargain compared to an equivalent triplet APO.

[bigjoe]

Couldn't agree more Wavy!!! Hi!
Even a smaller ETX125 I have is excellent for a lot of purposes. Its better all- round than a 4" ed I have . Sometimes I'd rather use it than a 10" SCT!!!
bigjoe

[bigjoe]

I to Adrian! And those big achros have one colour of out of focus in violet/blue light as Matt has stated also; ergo it cannot be super sharp as a Maksutov is.

PS: And hope you are enjoying your Mak.Dont forget its great for binaries too!
bigjoe.

[AG Hybrid]

Yeah mate, its tops. I am regularly amazed at how sharp the optics are. Especially after you factor in the purchase price. Synta/Skywatcher have been in the zone with these Mak's for years.

[bigjoe]

They are indeed surpring performers Adrian.
These Maks never cease ro amaze me.
bigjoe.

[Prickly]

As a visual filter I think it is very good and I enjoy using this on my diagonal for general viewing. I think it may help reduce light pollution slightly. I too have a NA140 vixen refractor. The filter doesn't correct enough for photographic. A UHCS or contrast booster eliminates more violet fringing but gives more colour cast for visual (ie contrast booster). That said I don't find the contrast booster too objectionable with its cast. The semi-apo adds nice contrast to Mars and planets like Jupiter, although as yet my NA140 hasn't lived up as well in the planetary space and probably needs more severe filtering. I'm yet to try the Baader 495 discussed above and am waiting to see how the contrast booster goes on Jupiter. Keep in mind my scope is f5.8 I think that in a f10 the semi apo may be enough.

Regards
David

[dannat]

a light yellow #8 does a good job, the baader 495 even better, the others like WO VR & semi apo take too uch light for me unless you're at 6"

[MattT]

I bought a 495 long pass a few weeks ago. It's the best CA remover I have tried. A slight yellow cast on Jupiter but that is quickly forgotten.
Interested to see how the contrast booster stacks up...semi apo fringe killer and WO v-1 are not as good as the 495.

Matt

[Prickly]

I think the light yellow is similar to the semi apo but the semi apo has no noticeable colour hue. Yes the semi apo filter cuts out light but mostly where you want it removed. There is good transmission (90% approx) for Ha, Hb and O3. But you will lose light in the yellow (light pollution region) and the blue (which causes the blue fringing). It doesn't cut out quite enough of the blue though. The contrast booster cuts in around 470 nm but the semi apo more at around 450. Looking through the semi apo I think it gives good light transmission in that it is not like looking through a nebular filter but you do get a bit more contrast. I'll have to see if I can track down a 495 filter at SPSP.

Note my comments are mainly based on suburban use with a 140mm refractor (pretty close to 6 inches)

Cheers
David