174mm with celestron OAG question - Forums

Topic starter

Nov 16, 2023

Howdy all. Question for those with the same setup.

i just used the 174mm mini on a celestron OAG, with an edge hd and .7 reducer for the first time. It was super dark. Like i could barely see the stars dark. It’s positioned before the filter wheel so that’s not the problem. It looked like the prisim was proper. I focused it during the day, and could peer through the OAG and see what I was pointing at without a problem. Should still I play with stalk height or is this normal?

I’m used to the 120mm mini on an f4 guidescope and it’s really bright.

even though it was so dark, it still found stars everywhere I pointed, and it guided between .25 and .5

¯\_(ツ)_/¯

Quinn Groessl

IOTD Staff

Nov 16, 2023

I have ZWO's OAG, but pretty much everything else about your post I had the same experience the past couple clear nights since I've gotten the 174mm mini. Last night I used bin 2 and PHD2 seemed to like that better.

Hans P. Strifeldt

Nov 16, 2023

Same experience here with my C8 EHD set-up at its debut. The "stars" even looked like bananas due to poor collimation. Still it tracked wonderfully wherever I pointed the scope - we're talking below 0.3 at its best. I guess that's what matters at the end of the day.

Richard Carande

Nov 17, 2023

I have a similar setup (on an Edge11) and experience, including being used to a nice bright image on my refractor f/4 guidescopes. Depending on the area of the sky I'm looking, I do have some issues sometimes finding a good guidestar. No problem imaging most galactic nebulae, within dense star fields, but looking away from the galactic plane, (most galaxies) can be an issue. I need to crank the 174 gain, use bin2 and even then sometimes there are no stars detected! I can will use Stellarium to try to find a better orientation for the OAG relative to the target, but then everything changes after the meridian flip. Fundamentally this issue is due to the slower speed of the "finder" and the fact that the OAG is working with dim light from the field edge. Also, I'm using a full-frame camera, ASI 2400, so I'm really on the edge and can't get closer to brighten the image without eclipsing the optical path to the main camera.

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Bruce Donzanti

Nov 17, 2023

Sean

I have been using the ASI174mm mini on the Celestron OAG on my C11" EdgeHD for several years with no problem. I've used it with and without the reducer and with many different sensor size cameras. Using PHD2 to guide, I have the 174mm set at 189 gain, bin 2 with noise reduction and I use a 2.5 sec exposure. A few thoughts: One, I am not sure what you mean by, " It’s positioned before the filter wheel…". The typical optical train is camera to FW to OAG to scope. Maybe that is what you mean and I just misunderstood. Two, you should not have to mess with moving the stalk once it is in the correct position, which is on the longer side of the sensor and just above it, so it does not interfere with light hitting the sensor. The only thing you should have to mess with is focusing it. This should give you a descent collection of stars to choose from to guide in most cases. I don't ever recall not having stars to guide unless my seeing/transparency conditions are poor.

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