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2 inch Baader Semi Apo filter.


oldfruit

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I have recently bought a Baader semi apo filter for use with my Evostar 150.

As we all know too well, we are always trying to find ways of improving the equipment that we have and having read many reviews (some good and some not) i thought that i would take the plunge and buy 2 inch version of this filter to enable me to put it into the diagonal to save faffing in the dark when changing eyepieces.

I am no expert but i was under no illusions about this filter from the start. I was not expecting my Evostar used with the filter to perform like a much more expensive scope.

All observation was done with a 12mm BST Explorer eyepiece giving 100x mag.

First target of the night was Vega. Without the filter it does focus to a nice point but there is a very noticable purple halo around the star. With the filter in place Vega still focuses nicely and the purple halo is minimal. It is still there but has been reduced by (i`m guessing) 60% so the view is more pleasing to the eye.

I then tried the double double in Lyra. There was never really any halo with these stars but i wanted to see if the view improved with the filter in place. To my eyes there was a very slight improvement and the gap between the components was visible with and without the filter but i thought the view with the filter just looked slightly sharper, but only slightly.

Albeiro next. I wanted to look at this pair to see if there was any effect on the colours using the filter. The orange star looked more orange than usual with the filter but the blue component was only showing a very slight blue colour, though this was expected as the filter blocks a lot of blue light.

The Moon was up so the next obvious target. I find the Moon through the refractor always nice and sharp but the limb and shadows on the terminator always show a strong purple edge. With the use of the semi apo filter there is only just a hint of the purple fringe. The image is still nice and sharp and the overall view is more pleasing to the eye. Also i should add, the Moon did look a very natural colour through the filter.

I am hoping to catch a view of Jupiter later as i primarily bought the filter for observing it and the Moon.

Was it a worthwhile buy at £85? Too early to say as tonight was the first time i have used it, though first impressions are good. It has given some improved views over use without the filter. I suppose it just depends how fussy you are about a bit of colour on the brighter objects.

Anyway, just thought i would share my findings and would be interested to hear from anyone else with experience of using this filter.

Clear skies.

Edited by oldfruit
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Just got the chance to look at Jupiter. Again most of the false colour had gone with the filter in use and there is an improvement with contrast. I think i am going to enjoy using this filter. :)

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Glad it's working out for you. I've got a starwave 80ED which might benefit from one of these but actually I've not had a problem with what I'm seeing through it

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Sounds like a good choice, I may invest one day for my 150 achro. Not quite as effective as a chromacorr but a lot cheaper. I tried a semi apo filter awhile ago on a semi apo zs80 and I found it gave a slight yellow tinge but worked very well

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Guest Ely Ellis

I was trying to get hold of the Semi-Apo filter a while ago, but I always missed out.

Now I have the Baader Contrast Booster and the Baader UHC filters, both 1 1/4"".

Both seem to be very good filters, but using them for looking at the moon, I found the UHC filter to give a very clear but purple image without fringing though.

The Contrast Booster did appear to be much superior than the UHC filter on the moon as it gave a very natural colour, like a brown dusty colour rather than bleached white as without any filter.

My scope is the Celestron 120mm Acro but when viewing the moon, I fit the lens cap on and remove the centre giving me an appature of around 50mm, this cuts down the light and improves contrast greatly.

I did post an image of the moon I took using the Contrast Booster (http://www.eastmidla...42-moon-stitch/), but I will post an image of the moon with both filters for comparison.

I do have a 2" Baader Fringe filter, I bought it to use on the 2" fitting of the scope, however it is unused because I didn't realise that the scopes 2" fitting was NOT threaded.

£50 plus P& P if anyone is interested.

Martin

Edited by Ely Ellis
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The Baader fringe killer and the contrast booster or uhc filters are all great filters in their own right. The reason that i opted for the semi apo filter was that i had read reviews that stated the image was much more natural looking through it.

As i said before, it all comes down to personal choice. For example, i have used various colour filters on Jupiter. Yes the filters change the colour but they also improve the view and help to enhance certain colours or features.

My wife was very patient last night and allowed me to show views with and without the filter. Even she said that she could see an improvement with the use of the filter.

I just wanted to try to enhance the view through the frac and it seems that the semi apo filter has done just that. I am very pleased with what i have seen so far but i shall be asking the guys at the next ELAC meet to give me honest opinions on the view with and without the filter.

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We will do that gladly Mark, shall I still bring that Contrast Booster as well for a check?

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Absolutely Ron. I have seen the view through the Contrast Booster (yours, thanks, :D ) and it was an improvement on the view without the filter. One of the main reasons that i bought the semi apo filter was to remove most of the false colour when i image Jupiter and yet still retain a natural looking image. I have yet to try this but i shall be posting results on here when the chance arises.

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Guest Ely Ellis

Comparison between the Baader Contrast Booster and UHC-S filters.

No processing has been done with either image other than re-sizeing.

(The blue one is UHC-S, the brown one is the Contrast Booster)

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Comparison between the Baader Contrast Booster and UHC-S filters.

No processing has been done with either image other than re-sizeing.

(The blue one is UHC-S, the brown one is the Contrast Booster)

They are really helpful results, i am suprised that the contrast booster image looks so natural as when i used it visually there was a definate yellowish hue to the view. Different scope etc etc. I should try images like this as it would be interesting to see what results i get.

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Guest Ely Ellis

Just for a little added information, both taken with exactly the same settings / conditions.

Camera: Olympus E500

ISO: 500

Shutter: 1/80 second

Celestron 120mm XLT refractor (Stopped down to 53mm)

1000m FL (F8.5). (Stopped down gives F19)

My personal preference between these two for use with the moon has to be the Contrast Booster. Focusing appeared to be less critical and the image was more pleasing.

I could not detect any fringing with either filter in place and little fringing without a filter.

This one below was done at a different date (hence near full moon), but same scope, FL and camera.

However ISO 640 & 1/160 sec was used for the exposure.

Edited by Ely Ellis
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