Hi Anurag & Deepak
My 1st name is also Anurag 😀
The question you've asked can't be solved by any one of us or yourself too in a quick way. Thus take your time to explore things until you have seen or know more about various options available and then choose the gear you feel comfortable and capable to do tasks you envisioned.
Read telescopes for astrophotography and mounts for astrophotography chapter in the following link. The resource is so well organized that you won't need to leave the website much to find any kind of technical information as a beginner and dslr owner. If you have any doubt, feel free to contact over forum as well as personally.
You will eventually learn that many other preferences apart from most imp that is budget, govern the telescope purchase. While reading about various designs available evaluate them on following basis.
1. The mount, its accuracy and its payload- Thus mount is even more important than telescope for AP. Thus scope's weight matters in its decision. Regarding mount itself, currently ioptron mounts are most innovative inlow/medium end and provide good own weight to payload ratio due to their z balance design. At higher end, many options. SCT/RC is the easiest scope to ride over load limited mount due to their limited length.
2. Portability- You need to go to dark sky places for imaging deep sky.
3. Frequent Upgrade vs lifelong instrument strategy- Something like apochromat refractors can keep you happy for many years for that focal length range which would be otherwise covered mostly by telephoto lenses from camera manufacturer brands. Whereas SCT or an intermediate fast newtonian (considering e.g. budget will be split in mount+scope) will serve as jack of all trades but eventually you will upgrade to proper astrophotography rig whose motorized focuser itself might cost more than budget you mentioned.
4. Focuser- Make sure the scope you choose has dual speed focuser.
5. focal reduction capabilty -at what focal ratio (or f numer as its said in general camera crowd jargon ), would you like to work at. That forces you to choose and plan field of view with your camera sensor as an input. If its crop dslr, fov is smaller. If its full frame, you need bigger field correction capability(at a higher cost)
6.Your existing setup and focal lengths already covered since you mention you have dslr.
7. Field correction- Coma correctors/flatteners with newtonians/refractors are common solutions to tame star shapes whereas RC/corrected SCT like Celestron Edge HD need specific reducers to tame focal ratios.
The list can go on but the basic rule that more is the diameter of objective more is the light gathering is true for everything.Design also dictates the usefulness of that aperture.
In my opinion, for beginners and budget considering other endless things that are more than telescope purchase itself like e.g. mount, field flattener/reducer, light pollution/narrowband filters, garden variety of adapters etc.
following options seem good enough to get started and be ready to try many things if you are starting from scratch.
i) 8 inch F/4 GSO Newtonain astrograph OTA with GSO coma corrector- good if you have APS-C dslr
iii) 8" RC telescope - Dedicated high focal length setup which requires reducer to speed up things.
For those who already own modest telescope, substitute 8 inch by 10 inch aperture and something like 5" to 6" refractor insted of 72mm to get some upgrade in visual astronomy too.
-Anurag Shevade