Hi,
How good is TS optics 8" f/4 Newtonian with carbon tube? any other recommendation from other Brands? want to use for imaging. I need focal length of 750mm to 800mm F ratio 4 or 5.
Thanks
Kimo
WTB- Newtonian (need help)
- orly_andico
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Re: WTB- Newtonian (need help)
The carbon tube is really for weight. Not strength. You will likely need to reinforce the tube under the focuser like I did. Frankly I'd go with the steel tube if it needs reinforcement anyway. Because carbon doesn't dent, it breaks.
You will want a Paracorr or the Baader Rowe corrector. Stay away from the MPCC, it adds spherical aberration. The Paracorr adds 15% focal length so an f4 becomes f4.6
The Rowe has no Barlow effect but has a lot of back focus.
At some point you may want to upgrade the focuser.
I have done all of these, and the result is decent. Large aperture, fast focal ratio, fairly inexpensive. But it's a big heavy wind grabber. My setup is over 15 kg.
You will want a Paracorr or the Baader Rowe corrector. Stay away from the MPCC, it adds spherical aberration. The Paracorr adds 15% focal length so an f4 becomes f4.6
The Rowe has no Barlow effect but has a lot of back focus.
At some point you may want to upgrade the focuser.
I have done all of these, and the result is decent. Large aperture, fast focal ratio, fairly inexpensive. But it's a big heavy wind grabber. My setup is over 15 kg.
Re: WTB- Newtonian (need help)
thanks. should I require coma corrector for small CCD like DSI 2?
many user comments bad and some good about 8" Newtonian with F/4. may be, good to go with 6" F/5 750mm with dual speed so its easy to collimate. its light weight and shouldn't have tilting problem right?
many user comments bad and some good about 8" Newtonian with F/4. may be, good to go with 6" F/5 750mm with dual speed so its easy to collimate. its light weight and shouldn't have tilting problem right?
- orly_andico
- Posts: 1616
- Joined: Sun Aug 09, 2009 11:14 pm
- Location: Braddell Heights
- Contact:
Re: WTB- Newtonian (need help)
I think the small sensor will not require a Paracorr. On my 8300 chip, the middle 20% of the sensor has round stars.
At f/4 collimation is rather critical. I am using a CatsEye XLKP and a TeleCat. And an Astrosystems barlowed laser.
I suspect a good laser with a barlow would suffice, the overkill collimation tools I have left over from my bad experiences at f/3 with the now-sold Keller reducer.
At f/4 collimation is rather critical. I am using a CatsEye XLKP and a TeleCat. And an Astrosystems barlowed laser.
I suspect a good laser with a barlow would suffice, the overkill collimation tools I have left over from my bad experiences at f/3 with the now-sold Keller reducer.