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Old 16-06-2024, 05:05 PM
Gezza
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Focal Reducer SAXON 909

Hi, have a Saxon novo 909 AZ3 ( Skywatcher Evostar 90). Focal length 910mm, Aperture 90mm, f10.1. Can anyone please recommend a focal reducer for this scope or if its even worth thinking about a focal reducer for this scope? thanks
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Old 16-06-2024, 05:56 PM
Saturnine (Jeff)
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Hi and Welcome to IIS.
First off, why do you think you need a focal reducer, you have a decent scope and mount for visual use, that scope being an achromat and on an AZ mount is not really suitable imaging, the main reason you may want a reducer. When observing, if you want a wider field of view just use a lower power eyepiece or one that has a wider apparent field of view. For visual use, for the same diameter objective lens telescope, a shorter focal ratio will not give a brighter image in the eyepiece.
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Old 16-06-2024, 08:40 PM
Gezza
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Thanks for the Welcome. I was going to purchase a EQ mount and look at some imaging in the future mainly planetary and Lunar so assumed a lower f ratio would help with the images. i currently have a 25mm, 10mm, and 5mm eyepiece and a 2 x Barlow, when you say a lower power eyepiece do you mean like a 32mm or 40mm? Thanks.
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Old 17-06-2024, 11:32 PM
Saturnine (Jeff)
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Hi Again
A 32mm eyepiece will give you 28X magnification, good for wider angle views of nebula and clusters. For close up lunar and planetary the 5mm should work well at 182X, which is reaching the normal limits of what your scope is capable of in anything but perfect seeing conditions.
For most types of astrophotography an EQ mount is a must and for your sized scope something in the EQ5 range would be a starting place. Be aware that your scope will introduce cromatic abberations, sometimes referred to as false colour, to your images, you may have noticed when looking at bright objects like the moon, that there is a blue fringe to the bright limb and the camera will exagerate that unless your are shooting in mono. An minus violet type filter will help alleviate the false colour to a moderate extent.
To get the planets in a decent image scale F ratios of F15 or more is needed, your 2X barlow will give you F20 which is fine but at an aperture of 90mm the image will be dimmed. What type of camera are you planning to use would be helpful to know. Also shooting the planets at lower F ratios will result in the planets disc being tiny, although brighter and that is for the larger targets of Jupiter and Saturn.
Hope this is of some help.

Cheers
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Old 18-06-2024, 11:34 PM
Gezza
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Hi again,
Thankyou all that Info has been a big help. An EQ 5 was the type of mount i was looking at so thanks for confirming thats what i should get. Yes I have noticed the blue fringe on the moon especially in the photo I took with my phone through the telescope so i will have a look at a minus violet filter. I just purchased off of this site a ASI120MC-S. Am I wanting too much from my first scope and should just wait till I can get a better imaging scope in the future and enjoy this for its visual aspects? Thanks again
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Old 19-06-2024, 12:39 AM
Saturnine (Jeff)
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Yes , you are probably expecting too much but count it as a learning curve. The ZWO120mc is a capable planetary & lunar camera and will be fine if and when you upgrade scopes. The Mono version would have been better, but then you would need RGB filters as well and that would've added another level of complexity.
The best Minus Violet filter is probably the Baader Semi Apo Filter, you really only need the 1 1/4" version, doesn't completely remove the blue fringing but reduces it a lot. Once you have an EQ mount treat the set up as an initiation into the dark arts of imaging and learn as much as you can about tracking and framing the object you want to image and what frame rates and gain settings work best for you. There is plenty of info and tutorials online for you to peruse to get you started. Just don't expect images like you see on here and elsewhere until you upgrade scopes but learn as much as you can in the meantime.
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Old 19-06-2024, 08:16 AM
Gezza
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Thankyou for all the advice it's been a great help.
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